Oh for fucks sakes. Artist/Illustrator-San, do not cut out visual ques like this. Show us what the kid did, don't just tell us. From my perspective, she fell and decided to kick him for laughing at her.
And before someone says "well you can just guess" I should remind you that this isn't the first time visual information has been denied, which makes it harder to tell if the scene is deliberate or a mistake, if the character made a correct or incorrect assessment. As far as I can tell, the story just wants us to think the kids are bad and that the MC is justifying in being a dick because all the story wants to do is just have an MC being a dick and needs to find a quick way to make them sympathetic in their actions.
Show don't tell