Drugs, you can drug her or yourself either way the situation will become more bareable.
You don't say how long you've been married, but if you are a newlywed and this is the first disagreement, then how you handle it will guide how the rest of your married life will be.
First, does your husband agree with his mother's comments and actions? If he doesn't know about them, YOU SHOULD TELL HIM because you need a united stand against unfair treatment. He should side with you (barring really unrealistic demands on your part) because he is married now!
Don't make the mistake I did 20+ years ago and bend over backwards "to keep the peace" and "because I'm nice" since the in-laws will smell weakness and walk all over you.
It is your right as an adult human being to confront her (nicely and diplomatically) and say that you heard certain things and wanted to check and see what SHE thought of them. If she attacks you, you have the right to throw her out of her house, and demand that your husband help you tell her that if she can't say something nice, not to say anything at all.
Keep in mind that there might be a misunderstanding and what you heard may not be accurate. She has the right to hear and correct mis-truths. Give her a chance to correct or apologize.
Just don't let her get away with the remarks because next time it may go a few steps further.
Believe me... I have two very difficult in-laws that have made my life a living hell and have learned the hard way from over two decades of trying to keep the peace. You have to stand up for yourself, honey. Don't let them de-value you!