Dabbling in magic for a break up is never a good way, sure you could try, but it could also back fire. Try sitting her down first, talk to her, and explain how YOU feel. If she loves you, she will listen, if she threatens to harm herself, just tell her how that hurts you as a friend, break up spells is never an answer.
Also, if she needs help emotionally, let her know you are there and that you care about her.
If she's depressed, tell her there are so many things that can help, you can even try happiness spells for her, but they'd work better if she casted them herself.
Even talking to people who suffered from depression or were suicidal helps on some. The Suicide Hotline does wonders for those in need.
I hope this helps, good luck and may the gods and goddesses guide you.