I'm going to refuse to accommodate my mother in law.
Why don't you want to accommodate her? Is there a problem with her?
Yeah, staying with her is like staying with a child for me.
I understand that it's not easy for you to stay with your mother in law, but you should consider the problems that you will be causing with your spouse if you refuse. Try your best to accommodate her instead.
But she's just so annoying.
I understand that you find her annoying to stay with, but you should try your best to get along with her for your spouse's sake. I'm sure they want the two of you to get along well.