i am sorry that your MIL is being a PITA
having had twins but she could be a really usefully ally when they are born- sounds like she likes to stick her nose into everything so use it to your advantage. get her to work out a cleaning/meal roster and co-ordinate it for your. get her to make sure that DH has his lunch everyday.
Get her busy- can man with twins on the way- the more help you can get the better.

Perhap she will have all the domestics and other boring jobs organised so you can just concentrate on your new little ones!!
use her enthusiasm to your advantage and you may be on to something. Perhaps a talk in boundaries might be in order, but make it out like it is someone else that is over stepping the boundaries and if she can help by making sure she tells that to respect your decisions and that you are doing what you think is best for you and your babies might help!!!
also tell her that you havent been receiving her emails lately as your email filter keeps thinking that all her emails are spam so for her to be careful what she sends so that i gets through to you
its a delicate sitaution but i reckon if you play her like a fiddle she would be a good person to work to your advantage
hugs