I apologize. I attempted to edit the post and ended up deleting it.
Basically, my mother's been pissing me off since my husband and I found out that we were pregnant. Since day one she's made it about her. Not one time has she said anything like you're going to be a good mother, or I'm so happy for you and your husband, or even said any motherly words of encouragement. Instead it's been calls out of the blue to say "you know what I was thinking? It's not about you or Joseph. I'M going to be a grandmother". Which is weird and sounds a bit childish. She also refers to me as "fatty" and "weeble wobble" and continues to do this even though I told her that I don't like it.
I asked her to wait at least a week or two after our daughter is born before her and my stepfather came to stay with us in our house for 2 weeks. She flipped a lid! She yelled about how this is supposed to be about Adele (my unborn child) and HER not me or my husband. All we're asking for is some time for us to bond as a new family or for me to be able to make my first attempts as a new mother without someone standing over my shoulder. She's made comments like if your daughter's "ugly" I'm not going to like her. She thought that was okay because she said it as a joke. She's told my grandmother that if our baby is ugly it'll be okay because she "can make ugly look cute". She says the weirdest and most insensitive this and thinks there's something wrong with ME when I get offended or upset or ask her to stop. I've tried to talk to her about all the above on numerous occasions and she tries to act as if SHE'S the victim. It's unbelievable.
OH AND THE WORST PART IS THAT SHE HAS REFERRED TO OUR UNBORN CHILD AND HER GRANDCHILD AS THE B WORD AND THOUGHT THAT WAS SUPPOSED TO BE FUNNY. I mean, AM I STUCK IN THE TWILIGHT ZONE!

Re: Vent - my mother
Set the rules, set them now. I beg my mom to come and stay for 2 weeks, but that's because she's a huge help. With our first we asked that no over night guests come the first week. I was worried DH would fade into the background and not learn to help with DD. It turned out I really needed my mom sooner, but we still waited it out.
In terms of your mom's attitude, if you don't get it in check now, it will only get worse. I had to tell my MIL she couldn't be around our girls on a regular basis because she wouldn't filter what she said. I gave specific examples (calling another grand daughter chunky monkey, thinking it's a fun game to make her daughter cry...etc). It felt hurtful to do, but protecting my children was more important than protecting her from the truth about her behavior.
I finally have time to check the board and miss this.
FML.
IMO she's not acting like a mother/grandmother so she shouldn't get special treatment/exemptions like one.
You can treat her like the bully she's being. Warn her that the more hurtful things she says, the worse the consequences. Ex. every time she's mean (and it's your definition of mean) it pushes back her visit by one day. Hold firm. If she acts out like child, treat her like a child.
My H & I will have to discuss this with my MIL in terms of her copious drinking/chain smoking. We have rules that she'll have to follow, like it or not. It's going to SUCK when we talk to her (she doesn't think she's an alcoholic & thinks her kids & SOs are exagerrating their sensitivity/disgust to the smell of cigarettes) but we've all banded together for the sake of our unborn children!
GL & stand your ground!
I would treat the situation like a tantruming toddler -- tell her what's expected behavior, set firm concrete limits, and stick to them as if your life depends on it. The LAST thing you want to teach either a toddler or a bully is that their behavior gets them what they want.
I suspect that just like toddler tantrums, her behavior will get WAY worse when you stand up to her. But hopefully with consistent reactions from you she'll learn that you have firm limits and will stop testing them as much eventually. Whatever you do, don't back down and let her "win" with inappropriate behavior or it will just drag out your suffering before she learns.