Why do you believe she is bipolar?
Bipolar is a complex disease and can not be dx'd based on 'mood swings'. Substance abuse alone could create similar symptoms / moodiness.
In order to be properly dx'd as bipolar she would need to be evaluated and it is not as simple as walking in the doctors office for 15 minutes.
How to get her to listen? Maybe the facility that she is in can begin the process of getting her evaluated or get a dx...whether it be what you feel it is or something else. It could be her substance abuse that is her problem.
~Zig