That's really quite sad. I hate it when I read stories like these. The one good thing to come out of this though is that the girl will now get some psychiatric treatment, as she obviously has some issues.
I wonder if her grades had anything to do with it though, could have just been the last straw. Maybe her parents are indeed pressuring her and maybe she is putting that pressure on herself, hopefully she will get the help she needs.
I never understand suicide anyway, I can't believe any situation is so bad that you can't see a way out and I think it is very selfish to your loved ones around you. A friend of mine tried to kill himself in December and it shook me up, but at the end of the day he was the one who had to help himself and get himself out of the s*it, no one else can.
Anyway, I hope she is okay and that it all works itself out.
Just be there for your brother, he'll need some support as he needs to support his girlfriend. Good luck.

Tash