ILADVOCATE said exactly what I was going to say. I agree what would help the most is for your mother to be educated about bipolar disorder. Maybe you could explain to her you want her to understand more about what you are going through, and you think the best way to do that is for her to learn more about the illness. When I was hospitalized they did a family meeting to help educate family members about bipolar and what warning signs to look for. If you are seeing a therapist maybe you should talk to him/her and see if you could arrange something like that for you and your mother.
Perhaps the best thing to do before discussing this with her is to inform her about bipolar in general.. Nami has good informational literature and also their friends and family support groups can be helpful as well. Also there are some books on the subject that can be of help in this regard. You can tell her somewhat about your own personal experience and concerns but it might be best to discuss the specifics with your psychiatrist.