Unfortunately, there are more details in this however in an effort to summarize my question I did include them.

She says she was forced into moving out of her living situation at the time into a new apartment that her parents (mom mainly) said that she'd help out because she knew her daughter was going to school full-time while working a part-time job. And again I reiterate, there was no agreement of interest or even a repayment of funds.

The car situation is this, my fiance' bought this car outright with her own cash she had saved at around 17. At 19 she was able to buy a another vehicle with her own cash and decided to sell her first car to her mom. Moving forward, she gets in a accident and the second car is totaled. Her mom then says she can use the first car and/or purchase it. However they never came to an agreed price before her mom signed over the title to my fiance'. On the paperwork it states "Gift".

Look, I'm encouraging my fiance' to pay back what she legally owes but NOT interest her mom wants to tack on...just because. That's not right. I'm simply asking if her mom can legally sue for interest charges, which I could see her doing, because she's that type of person.