Well she's obviously a woman who bore a child... Not a huge deal. And I consider just about all clothing disposable. If I was getting free daycare and laundry service in my home I'd pitch the undies.
When I was a "nanny" in college...I took care of the baby, did the laundry, the dusting, the vacuuming and even the grocery shopping...for $5.00 an hour!!! (In between classes, studying, etc.) Boy, have times changed!
It sounds like the husband does not have a problem with the way his mother takes care of his home and children. If she has a problem with it, I would think it would be up to her to fix it. It's not a matter of the husband having respect for the wife, the wife should have enough respect for the MIL to speak to her as an adult, no matter how "difficult" it is. Everybody Loves Raymond is a sitcom, this is real life, deal with it, even if it is uncomfortable. The MIL is doing a very kind thing/service, she doesn't deserve to be called names and be spoken about behind her back.