Most Helpful Guy
Don't commit suicide, your life has purpose no matter what.
Now with the boyfriend issue, I'll be frank - Fuck him he's a jerk. AND if he's truly a jerk like you say, warn your best friend but don't control what she does if she wants to not acknowledge your warnings she has to learn the hard way.
Most Helpful Girl
Doesn't your "best friend" know why you broke up with that guy in the first place? Maybe try to talk to her about this and see why she is so interested in him after what he did. She should know better than that but I have seen relationships between people get ruined just over a guy.