What does your husband do and say? You're his wife, and it's his mother, so he should be supporting you and speaking to his mother. He should insist she respect you and not insult you. He should expect her to pay rent.

Yes, you do support your household, caring for the children and taking care of the house. But I wouldn't care if you didn't. It's your home and your husband's, and it's not hers. You two get to make the rules, even if she doesn't like them and thinks they're unfair. Your husband should tell her that if she doesn't pay rent, she needs to find another place. For that matter, she needs to find another place, period.

A couple of things I recommend is that you don't cook, clean or do laundry for her. It may seem easier to do it and avoid further conflict, but you need some control over the situation. If your husband supports you like he should, he won't do it for her, either. At the very least, let her do those things for herself. She isn't paying rent or buying food, so force her to contribute. Or maybe she'll go out to eat, and you'll have a few minutes of peace.

Make some rules and stick to them.