My niece used my Mom house to open a Business she had her name put on Mom house, Mom made a Will to leave the house in my name but Mom passed before the Will came back from the Lawyers. Can my niece put the house in probate or have it forclosed. Can I have her pay her share of the loan back,and I'll pay mom share and put the house in my name. Please help me.

Depends on who the niece name is on the house, if they were put on with right of suv. Then she may just own the house and it does not have to go into probate.

If not, and they were just joint owners, the mom's heir will own 1/2 of the house and she will own the other.

But niece part of the house does not go into probate, only the share of the house ( unless the deed gives it to niece at death)

But you need to find out how the current deed is listed