I have so many friends and relatives with this exact same problem. The first thing to know is that your MIL doesn't have a dislike for YOU, she will dislike anyone that is taking her precious baby from her,(in her mind), it just so happens to be you. It's not about you at all, it's about control and that's she's lost that control over her son. I would really take this lesson and if you have a boy, do not do the same thing to him. Embrace who he's ends up with no matter what or you will be the one being excluded from things! This one hits home to me because I am about to have 3 boys.
In this case, I do think it's your DH's place to say something, and you need not. He should tell her that he doesn't appreciate how she treats you and that you are his wife and tell her how much he loves and cares for you and your daughter. He should also tell her that if she cannot show respect for you and get along that she won't get to see him or her soon to be grandchild often because he cannot tolerate her disrespecting his wife. This all should be said gently and not in an accusing or angry tone. Let her react however she wants even if she denys it, just stick to your guns, the both of you.If she does deny it, then go on and invite her next time and if she does disrespect you/treat you badly, then some distance for awhile should let her know that your husband really meant what he said. And no more fighting about it! MIL's like this love to get their son's fighting about this kind of thing with their wives. Also, don't let her do the guilt trip thing, it will only validate to her that she's "right".