I personally don't see a problem with her asking if those dates are okay to visit, at least she is asking and not just showing up. you could always say no. and maybe she is really trying to make an effort. i think you have to decide if you would like to try to have a relationship with your mil or if you'd rather not because she's been such a beotch to you in the past.
That being said, i get a long with my fmil really well maybe my opinion would be different if i didn't.