Pushing her up against a wall to kiss her must kinda hurt. Just think, you're there, trying to enjoy the kiss and then bam - spine crushed up against a concrete wall. Would her vertabrae aprecciate it? I think not.
Also, she's not indestructable. She's gonna break. Think of that next take you go making out up against hard structures...ew that sounded gross. But did you know you can be paralyzed if you hurt your spine in a certain way?
And usually this boy is meant to be like a couple inches taller than her, which probably means he's stronger than her which probably means he'll be kinda rough. So yeah.
(dedicated to @LuckyLavender thanks gurl)