That ending....was cold. That set me off. Not being acknowledged after a greeting when clearly taking notice (ffs, she turned towards him) breaks any future civilised endeavours. You lost a friend.
Guys, no, no. She overheard him saying that his grades dropped and thinks it's her fault. She's mad at herself more than anything. Also mad at him for not saying anything about it - he shouldn't have spent so much time on her and worked on his own studies instead.
Right now she thinks she's being a bad influence, so she's trying to put some distance between them for his sake.