I'm mad at my mother-in-law and making the family visit awkward
Why are you mad at her?
The bitch is always so annoying, talking about stupid things
It's cool, man, no need to be so angry over the words of another person. If she says things you don't like, ignore her or leave.
I can't leave because I promised my wife I'd stay.
If you can't leave, then I think you should just not pay attention to what she says. Focus your attention on something else, like a person who you do like talking to. Making a scene isn't going to help anything.