What is wrong with my mother-in-law?

I think my MIL has bipolar or either she is borderline personality. It is getting to the point where no one wants to be around her. She is running her friends and family away. She lies alot and blames other people for stuff. Like she'll say something and say someone else said it. She is so negative too and is uninterested in things.. and sometimes everything has to be all about her. Like when I lost some weight after my baby, she didn't say good job, she just starts in about her weight. She sounds depressed and talks about how lonely she is. She has been talking about my mom and I think she is jealous. We just had a baby 8 months ago and she is acting over obsessive and controlling-like she is the mother. So we confronted her about talking about my mom behind her back(someone told us) and she first denied it & then started getting defensive and started cursing. We have caught her in so many lies lately. There's no telling how long she has been lying. Anyway, she shows alot of the clic signs like talking alot, talking fast and she switches from one subject to the next, she also cuts people off when they are talking. And she is very forgetful sometimes and has trouble thinking -like when you are in a conversation she will forget what she is saying mid-sentence - i guess because she is thinking about what she wants to say next. She also doesn't sleep much. She can go to bed at 12 or 1 am and get up after about 4-5 hrs and feel rested. My husband & I don't care to be around her because she is selfish, miserable, lies, and she talks about people BAD!! Just her mood is enough to bring you down. She's always down in the dumps. What do u think??