T.M.
Boy does this hit a button for me. MY MIL is exactly like this. The thing is that I don't mind! I find the woman and her opinions to be unbearable. I never see her either nor does she want to see my daughter that often. Only on holidays or when my hubby takes our daughter over to see her. I like that way. However, that's just me. I don't want her to have any unnecessary influence on my daughter.
Now my mom on the other hand would love to see my daughter more, but we leave two states away!
I would just keep putting out invitations but not take it personally if you don't see her. If your husband doesn't make a big deal out of her seeing your child, then just let it go. Maybe as your son gets older she may show more interest? If not, again, don't take it to heart.