Simple, tell her no. She shouldnt have sold her damn house without talkng to you about it. Let her go buy a new house with the money from the sale of her old one.

So your wife can't stand her own mother?

Pick her up along with 7 days worth of clothing (for her), then drop her off at the cheapest and worse care home you can find.

she can't move in with you if you don't let her so just tell her no and leave it at that.

this is a case for Dear Abby

tell her no and if she insists, call the police on her, she for trespassing.

"mother-in-maw" is the best way that phrase could possibly have been misspelled.

Tell her the marriage is still young and you're too busy banging all over the house and you want to enjoy an actual effing relationship with the person you love before all your time gets consumed by little monsters. It's kind of critical for you guys to get your shit sorted and just have a few years to settle, enjoy each other's company, and master running a household without the stress of a grouchy old freeloader with no respect for you, your relationship, or your home. "Surprise, I am moving in!" "No, surprise, I will light you on fire". If she had financial issues, she should have asked politely and made plans that you guys agreed to. She will wear out her welcome by the time she needs her diapers changed and be stuck in a home away from family, is that really what she wants?

Grow a pair and dont let her.

Just don't let her. It's your house, she doesn't get to decide that she's going to live there, you get to decide that. Who cares if it pisses her off.