Can a private owner legally repossess his or her car?

Repossession rights require that the original contract reserved a security interest in the car and that security interest must be recorded. I am willing to wager that there was no recorded security interest. However, if she sues for nonpayment of the contract, she can win because she agreed to give you the car and title in exchange for money and you got the car and title. Doesn't matter how she got it to you.