FMIL VENT

look on the bright side... at least she likes you... if shes set in her ways, then just keep on her good side and dont pay attention to all the negative things she says...its not a reflection of you anyways..

Ughhh! Sounds like it's all about 'me, me, me' with her
What if you (very nicely) told her how glad you are to be coming into JT's family, and that you just don't feel comfortable with listening to her talk that way about FSIL because you think of them ALL as your family and your family doesn't do things that way...? I don't know if that really sounds right, but I'm sure you get my point.

Yeah, I am definitely going to have to say something to her, but she even puts down her daughter to her face and then says things like, 'Mary, Rachel would never do something that stupid, you could learn something from her.' WHO SAYS THINGS LIKE THAT? I mean, FSIL knows what a nut her mother is,too, and we get along really well, but her mother is out of control. The thing is, I usually tell her what's on my mind and how I feel about things honestly, and I think she likes me because I am the ONLY one who tells her like it is. Like, I can tell her when she's being crazy, hence the fact that I call her Crazy Lady. But, in this situation, it is too personal to say anything. I don't know how to. I'll just have to think a little harder....

That stinks because even though your FSIL knows that her mother is a 'crazy lady' , do you think she could become resentful of her mother always comparing you and her??
Maybe you could take that stance with your FMIL

Yeah, that's what I was thinking too. See? Great minds think alike!