HJ::

Jyn was sitting on the third higher branch of a tree - which is located at approximately three feets from the black lake. The orphan child had always loved silence and nature, and she'd never understood why people use their tongues to speak and say nothing. Because that was a very big annoying problem for Jyn. She'd prefer to say nothing rather than speaking to say nothing, really. Anyway, she didn't even understand people, and they didn't understand her. It was better for her to remain alone, for sure. And there she was, in her tree. It was her favorite, don't ask why, she didn't even know. Since her first year at Hogwart, she came here and look at the sky, at the lake, at the life spreading itself around her. She didn't know why she loved nature that much, as she didn't know anything about her real family, but it was that special thing inside her that made her feel alive for once. The dark and gloomy walls of the school were oppressive and creepy. But she was a mysterious freak anyway. Jyn did assume she was the only living person to hate Hogwart, and maybe inside her, she was quite happy about that particular feature.
And here are now coming students. She's far from them, and as she wants to have nothing to do with them, she doesn't event try to recognize the girls. Because there are girls, two by the way. She doesn't care.

HJ:

Dave had decided that today was the day he'd declare his love and devotion for the most amazing creature in Hogwarts and the world itself — and believe it or not, this creature wasn't a crup or some kind of freak, but a regular human being... If Wilda Griffiths was to be considered a regular human being, for she was nothing but incredible in Dave's eyes. This declaration wasn't truly planned, for the Gryffindor was very shy when it came to talk about feelings, but when Rosalyn Weasley taught him there were reductions in fireworks prices at Zonko's Joke Shop, he realized he couldn't find a better way of revealing his sparkling love to the Ravenclaw than a huge and noisy display of colourful firecrackers. The day after this epiphany, Dave Goujon ended up very poor in galleons but so rich in fireworks his roomates suddenly worried he might blow their dormitory up : in order to calm them, and also because he now was in such a hurry to put his plan into effect, he agreed to implement it the soonest he could. And the soonest was about to be now, for he saw like five minutes earlier his beloved bird leaving the castle, her cape on her shoulders, that he considered to be the proof she'd stay outside for a while. The second after, Dave was running through Hogwarts to fetch his equipment he had the greatest harm to move from the top of the Gryffindor Tower to the park. But it's well known that love lends wings, and Dave eventually succeeded in leaving the castle with his huge box full of fireworks, frantically looking for Wilda. It took him a few seconds to locate her sitting under a tree with a friend, near the lake. Dave, who was far enough from the girls so they can't understand what he was up to, started to take his fireworks out of the box in order to align it on the floor with the greatest care.

Jyn was the kind of girl who couldn’t fit anywhere and didn’t want to fit anywhere. She didn’t like people, people didn’t like her, and everything was going on. There, on her branch, no one would be worried about her. She didn’t have any friends, and her parents couldn’t send her letters because they are not wizards. The postman doesn’t go at Hogwart obviously. But most people are not like her, and that’s probably a good thing - for them, not her - as she sees people coming under her tree. She remarks two girls, and she believes she knows one of them, but she’s not quite sure about that. Then, she hears one talks and yes, she knows her. The orphan child blinks her blue eyes to be sure of what she’s seeing. Wilda Griffiths is the kind of student you cannot ignore, because she’s a talkative and an enthusiastic girl - thank you so much. A long time ago - last week - Jyn and her had to train magic with their damned sticks and the Hufflepuff didn’t make any try or endeavour.

Jyn doesn’t like to hear talks. Because they are mostly nonsence. People talk about the whether, about the teachers, about their marks, about their families, but that is odd she thinks. As an aloof,  and strange child - according to the teachers, the students, the children and all the human beings. She's quite sure Ambrosius Flint thinks the same and she’s sad about that. This boy is the only one she wants to impress. On her right knee, there’s a bruise and she’s just tipping on it to try it. But suddenly, she hears an explosion, and feels the fatefull blast. Anxious about that - like the savage animal she is - she grabs the branch and stands up to see what’s going on. and there, in the sky, is a firework. She lets out a grunt as she sees everything. She tenses her jaw. That’s ridiculous.

One hundred and thirty four. He had in his possession one hundred and thirty four fireworks of different colors and different effects. Some of them where like swirling rockets, others like colourful bombs, and even one - the most important !- would draw in the air in illuminated letters a message he wrote himself (you can easily guess what it is !), but Dave was certain Wilda would love them all equally. The problem was that it was way more complicated to grant them in order for them not to explode at the very same time. The Gryffindor had a more or less precise idea of which fireworks he wanted to explode first, but he soon realized he had no idea of the way he could manage the all thing. The all hundred and thirty four of them. What if he just lit the most important one, the "I love you Wilda Griffiths, Dave", and kept the others for later ? He remembered almost immediately his roomies faces' and gave up this idea : he had to burn it all tonight, and for he needed considerable time to ensure the show he had to begin right know. Dave pulled his wand out of his pocket and drove it to a big firework he didn't remember how it'll explode, and...
— Incendio ! he cast, and immediatly an open flame shot up and inflamed the fuse. As a precaution, Dave took a few steps forward and watched the firework rising off the ground with a thunderous roar, and was to the point of congratulating himself for his efforts when he realized the first firework burnt the others around, that started to blaze eagerly and take off as well.
— Oh no no no ! he cried out when he saw his I love you Wilda's firework burning, for it was not at all the moment for such a declaration, but the moment he reached it, he just had the opportunity to shade his eyes for the firework was rising off among the others. Dave, at the very moment, was really disappointed... and then he saw another firework hit the tree Wilda and her friend they were seat under, the very moment his loving message popped up in the sky.
— Oh crap, he just said, highly conscious he was in a deep, deep Thestral's shit.

Jyn doesn't really understand how much it's important for people to express their love. She doesn't at all - even though she tried once - because she's shy and worried to be ridiculous. There are many ways to show someone we love him, and obviously, on that evening, someone is trying. Using an odd way. On her tree, hypnotized by the colours around, Jyn Dawkins doesn't see a firework hitting HER tree in WHICH she's  sitting. There is a muffled sound above her, but she doesn't have the time to raise her eyes. Abruptly, she falls of her tree, and is burnt on her right leg. She doesn't shout out anything, her fall is soundless, silent like this evening should be, and the Hufflepuff lands on the girls sitting under the tree.
As Jyn didn't see anything except the colours of the fireworks, she doesn't know where they're from. She doesn't know who fired them up, so she concludes Wilda and her-weird-and-unknown-friend turned them on. "That's both of you !" she assesses. She doesn't say anything else, but casts out : "LIMACIUS ERUCTO". Jyn doesn't wait for more, and she flees, her specialty.

Spoiler:

HJ:

From the top of his promontory, the Gryffindor saw that something dropped out of the tree because all of the sudden they were three of them under the branches : and because obviously there weren't enough lights with the fireworks in the park, a colorfull ray of light passed through the air and an amazed Dave saw Jyn Dawkings fleeing the scene under the explosions. The boy had an irresistible laugh by imagining she was the one who felt of the tree (what on earth was she doing here after all ?), but soon his laugh got stuck in his throat as he realized the crazy kid was running in his direction. It was too good an opportunity to make fun of her, so Dave decided not to hide his glorious feat and tried to catch her attention as she was running straight away to the castle.
— Hey Jyn ! he cried with a loud voice, completely oblivious of the fact he just nearly killed three girls a few seconds ago, and litterally signed his mischief, and that they'd just know for sure he was guilty after all that noise he made. What happened to you ? You look pissed ! Was she really ?

The little Hufflepuff was not a patient girl. Anyone knowing about her would know that. She was a baffling child. With her leg burnt and the scared the felt, she didn't want to speak, or try to understand anything. She didn't see the message, she only saw two girls and a firework. There was nothing to understand. Wilda was abruptly hit by her spell and she fled. She crossed Dave on her way back to the castle. And obviously, as he's a common idiot, he decided to call her. Amazing evening. "Fuck you !" she answered badly. "Fuck y'all !" she cried out again. Big tears were on her red cheeks, her leg was astonishingly painful. She just didn't want to talk to him right now, he was just a stupid boy... She hates him. She hates him so much. Clearly, like everyone else.