Is it okay for my girlfriend to do this?

[SheChasesComets]

No, it's really not okay for her to do anything like that to you.

Whether you spent a lot or not on her doesn't matter. It's the thought that counts, and the fact that she threw your flowers to the floor and disregarded them speaks volumes. She's high maintenance and not good for you, at all. Next is the statuses - she's likely turned friends against you, and seems deluded. Thirdly, she is actually physically violent towards you, which states that she doesn't respect or deserve you. She's also cheated. Please, please don't stay with her. Yes, there's the brother aspect, and you're scared, but seriously, tell an adult. Your mother, father, anyone. If you still go to school, tell your teachers. Just break up with her quietly - personally, I wouldn't give her the dignity of an in-person breakup, but that's just me. Make sure you're safe. The worst comes to the worst, it's probably an empty threat.

Good luck.