Can MIL legally force us to sign our house over to her after we pay it off?

My husband and I live on a property with 2 houses. Ours is considered the guest house. His stepmother and younger siblings live in the main house.

The house was originally hers, but she lost it, so a family friend stepped in to help by buying the property and renting it to her. She didn’t pay, so they decided to sell, and she told everyone they betrayed her.

She then asked my husband (who didn’t have all the facts because she lied) to step in and secure a loan in his name, having him buy the house until her credit recovers and she can repurchase the house from him. She advertised it as being a short term arrangement because she was earning her degree and planning on getting a better job. Currently, the mortgage is only in his name, and she is on the deed with rights to survivorship. My husband agreed as she was heavily pressuring him to save the family and he wanted to protect his siblings. He wound up paying significantly more than she did when she bought it. This was in 2022.

They were to split the mortgage 50/50 (although the main house is more than twice as large as the guesthouse and in far better condition). She then didn’t pay for 9 months.

In 2023, when my husband and I were dating, nearly a year after the purchase and 8 days after I moved in, she demanded that he sign a contract saying he agrees to transfer “full ownership” to her when she secures a loan for the remaining balance and that she agrees to him having ownership of the guesthouse. It also states that neither of them can sell the house or have a 3rd party enter the agreement (this was done to block me from having any involvement or being able to be on the deed), or break any part of the agreement. It says “This agreement is contingent upon both parties’ equal payment of half the payoff figure from each party until loan is paid off in its entirety.” It also mentions she is to pay back the 9 months of non-payment from 2022. Again, he felt pressured and signed it because she was creating a lot of emotional turmoil as soon as I moved in (calling him at work in hysterics, crying, etc.)

It’s now 2025 and not only is she nowhere near repairing her credit, but she’s been unemployed the majority of the time, and from what we can tell is receiving some kind of state benefits and borrowing from her family while saying she’s looking for a job (She rejects all opportunities she gets). The mortgage is due on the 1st and she refuses to pay until the 15th or later, so we’re essentially covering her half until she reimburses us. We’re now on month 3 in a row of her not paying her full half, just part.

I’m just wondering how legitimate her contract is given all the inconsistencies. I don’t imagine a bank is going to issue a loan to someone for a house they already legally own, especially if it’s not for sale and per the contract, can’t be. She also appears in violation of the contract as is with how many missed and partial payments she has. My fear is someday we will have paid it off and have nothing except the money from the 9 months owed or that she will somehow secure a loan when the balance is nearly paid off and force us to sign everything over.

Does a contract like this really hold any weight? What does this all look like from a legal standpoint?

Location: GA, USA