I think my mom has bipolar disorder?

There may be many reasons for your mother's behavior. Since she is in her 50's, she may have worse mood swings due to menopause. Hormones would account for it getting worse the past year or two. Bipolar disorder usually is marked by periods of mania -- overly talkative, happy, need for little sleep, overspending money, etc. Let her know that your are simply concerned that she feel the best that she can for herself. Encourage her to talk with another woman friend or see her physician. Invite her on a walk with you and such, as exercise is very good for helping stabilize moods. Find ways to be gentle about pointing out symptoms. It's very difficult for parents to admit their children that something may be wrong. Keep caring.