I think my daughter is suicidal?

What you need to do is sit down with her and have a polite and gentle conversation. Make sure you're in a relaxed pose and speak calmly. Tell her that you're still going to help her with college and reure her that you're there for her and that you love her. All children want to know is that they're loved. She probably feels betrayed and used. You need to show her you still care.