What about this approach? Make it into a favor. Tell her that your mom will be coming for the first two weeks (or whatever) and it would be so much more help for you if she would come the next two weeks (or whatever) because that's when you will really, really need her. Tell her you are scared that if you have all this help (MIL and mother) for two weeks and then you are just abandoned, you are not sure how you will handle it, but if your mom and MIL could switch off instead, you'd feel a ton more confident.
Basically, it's all about puffing her up and kissing her butt and making her feel needed instead of rejected. I know you don't think she's much help, but I bet she THINKS she helps out, so your logic will make sense to her. And maybe if she gets it in her head in advance that she is "going to help her DIL" and she says it that way to all her friends, she really will be more help.
Basically, it's all about puffing her up and kissing her butt and making her feel needed instead of rejected. I know you don't think she's much help, but I bet she THINKS she helps out, so your logic will make sense to her. And maybe if she gets it in her head in advance that she is "going to help her DIL" and she says it that way to all her friends, she really will be more help.