She really isn't in her right mind. She needs to get her bipolar disorder under control or she won't be able to be a good parent. And bipolar disorder really is easily controlled with the proper medication, provided she takes the medication regularly.
I know it hurts. Believe me, I know. I've had experience, 20 years of it. But it's very hard to get mad at someone when you know they genuinely aren't responsible for their own actions, that they just can't help it. But she has a child, she needs to get medical/psychiatric help so she can be a responsible parent.
