Please keep in mind that this is someone you've only lived with and I assume even known for three months. Bipolar disorder is a very serious mental illness and not easily diagnosed. It's definitely not your place to call her parents or talk with her about having a mental illness. This type of action runs the risk of potentially doing more harm than good due to the stigma associated with mental health disorders.
Set firm boundaries regarding your living together and what is needed for both of you to be successful. I would keep your word choice to behavioral language. What I mean is describe behavior and actions and how they affect you. Frame things in a positive way. "Hey roomie, I really need your help with something. Do you think you could give me a little quiet time in the room to get some studying done, this class is really kicking my tail and I need to do well to keep my parent's off my back."
The most important thing to keep in mind is that you can not control others, but you can control yourself. If she fails to respond to the attempts you make to set boundaries then change your routines to make them successful for you. It may mean you spend less time in your room and she could interpret this as you avoiding her, but just be honest. There's nothing wrong with saying, "It's hard for me to get any studying done in the room and so I've started doing xyz. It's nothing personal, I've just got to make my grades a priority."