Is cocain dangerous to Bipolar Disorder sufferers?

My best friend who suffers from bipolar disorder decided to take herself off of her medication a few months back because she said she felt better in herself then she went out to a party and got drunk and took cocaine and had a one night stand (with a guy she knew)? She felt really bad afterwards and was really depressed for the next few weeks after.. was the cocaine really bad for her because she came off her meds?