Best Friends Conflict

Ok so my best friend has a conflict with two guys and I have no idea what to tell her. Two guys like her. Person A is the one she's liked for a while and Person B she just recently started to like, but he wants to start a relationship with her. Her guy tells her Person B, but if she breaks off whatever she has with Person A, he'll become even more depressed and sucicidal then he already is. What should she do? What should I tell her?