Dad Forcing My Mom To Sell The House For His Equity—what Are Her Legal Grounds?

Divorce law but I’d say more applicable to real estate.

Quick facts: -parents divorced in 2008 -divorce agreement that after all the kids graduated, she would sell the house and it would be split (this would be around… 2017?) -stipulation that he would help maintain the house until then

In 2010 my dad didn’t want to pay taxes on his new home as a “second home” so he signed the deed to my mom and the mortgage was in her name. Since then, she has been solely responsible for the home and maintenance and he never helped (new roof, groundwork, etc)

She has since become disabled after an accident and hasn’t been able to regain capabilities to work—so her income is limited but she paid off the house so her bills are low.

My dad is now insisting he’s entitled to have her sell the house for his gain in equity per the divorce. Since he put the deed and mortgage in her name and didn’t maintain his responsibility, did he violate the terms and make it null?

She is obviously not in a position to move and doesn’t have much money after her medical expenses from the accident, so I am very worried.

He wants her to sell it since he wants to buy a house with his new wife.