Is it normal that i don't like my mother in law?

I am engaged to a great guy. We've been together for years now & we're very happy. The only "problem" is his jealous, controlling, bitchy mother. She never gave me a chance and she's jealous because she wants all his attention, money and for him to hang on to her every word! She's divorced, unemployed, fat and not happy with her own life. She has another son who she doesn't try to control because he's not having it. But my fiancé wants to make her happy and keep the peace. Now she wants us to come to her house which she hasn't asked before and I told my fiancé that although I'd never be mean or rude to her, I don't want to be around her. I'm over it,I'm done trying! And my fiancé thinks I'm being unfair to a woman that I went out of my way to e nice to & she gave me her fat ass to kiss!! Shes barely spoken to me! Now that she's ready to get her head outta her ass I'm supposed to be all for it?! I don't think so!