What's wrong with my mother-in-law and her children?

My mother-in-law's behavior, as well as that of her children baffles me. I don't think she wants her son and I to be happy. One Christmas she asked me if I got all that I wanted and I said, well, I have my husband and our baby, and that's the best present I could have. Instead of smiling and thinking that was a good thing to say, she got really silent, then said, Oh! Another time I said I loved shopping for clothes for my husband and she got mad and told me not to do that. Hello! Why not? Another time she was at our home and complaining about some bad habit of her husband's, then she said oh, I know that this or that must get on your nerves about my son. Well I said nothing in response to that because I couldn't understand why she would want me to complain to her about his annoying habits. Another time she asked how we were doing and I said fine. She said, "really? Are you sure? She always seems to be fishing for something. If she gets a hold of anything, she runs with it and tells the rest of the family members. And if I say something she doesn't like, she calls the one person in the family who she knows hates me and tells the person about it--complaining and gossiping about me. I found out because the person calls the house and bad mouths me to my husband about things they would know nothing about since they did not hear the conversation. She picks fights with me over stupid stuff, attacks what I say when she doesn't like it, but NEVER says anything to her own children when they curse out my husband. And then she gets mad when I don't want to chat with her on the phone. She also tells me I'm afraid of certain family members and that's why I don't want time with them. I made it very clear that I'm not afraid of them, but I that I choose not to spend time with people who are mean and do not like me. She simply doesn't get why I don't like being bullied and abused by her and the rest of the family. When we told her we were expecting, she initially did not seem happy. In fact, she seemed indifferent. It was only a while later that she acted happy. When she met the baby, she did not act like a normal grandmother and look happy. Instead she was frowning and hurling insults like, "The baby is going to be spoiled. The baby is a handful, and The baby has boogers in its nose. " She yells at me for not influencing her son to do what she wants him to do... and on and on it goes. All of this behavior is very confusing to me. If I'm around, they're mad that I'm around. When I'm not around, they're talking about me behind my back. I told them that if any of them have something to say to me, please say it to my face. But not one of them will. The one who hates me refuses to tell me why and refuses to be respectful to me, even though his brother has asked him to. He says he will not do it and will not keep in touch if he can't be disrespectful to me. He became angry also because I would not let another sibling be rude to me. There is something very, very wrong; and I don't know what it is. One minute it seems she misses us and wants a connection with both of us, then the next it's all this craziness. Can anyone give me a clue about what is going on here?