You said it yourself, her friend has given up and stopped writing. There are other ways to help her with that, but the way she did it is just wrong and insensitive. She should've known that her friend is not exactly in her "right mind" and is feeling down in the dumps. It's no brainer that what she did is incredibly dumb, she should've thought about what her friend would feel. First of all, her friend didn't ask for her help. Even if she did want to help her, she could've at least voiced her concern for her friend first before doing anything like what she did.
It wasn't FL's fault things are the way they are, yes. But she should've thought first before she acted. PD himself also scolded her for thinking the way she did, but it fell on deaf ears. She was too bullheaded and immature. It's good that she does know now that she was wrong.
Actually You right. She is really dumb. But I don't like it when she feels guilty while writing a novel
It could have been a shout instead of a slap, but the slap felt too heavy for me. FL is under a lot of pressure; she's living out her best friend's dream, which makes her feel guilty (though she really shouldn't). It's clear that her friend isn't happy about it either. This situation isn't fair to FL, and I know it must be painful for her friend. But she has given up and stopped writing. I understand that FL might be acting thoughtlessly and that her actions could be seen as disrespectful, but she’s just trying to make her friend happy.