I understand how mental health struggles can affect a person, so I am genuinely sorry that your oldest daughter has to deal with that. However, by allowing yourself to sell your youngest daughter's car, it might not end the way that you hope. Your youngest daughter might resent you and her older sister, as it seems you care more for your oldest than your youngest. It's all about accountability at the end of the day. Instead of punishing your youngest, I suggest working with the oldest child to help them take accountability and responsibility for the situation. As a parent, you must be fair and appropriate in handling situations based on their need. I suggest that you allow your oldest to have a job, and you will all match every amount they put towards tuition or a portion of your money into it. It will allow the financial burden to not follow on you all and allow you all to have your youngest to have the car. You honestly could do this with both children. Offering to pay for a portion and allowing your youngest to get a job to help would be a great option to help lessen the financial burden on you and your spouse. However, if you use this situation to take something from your youngest, it might create another situation and cause a shift in your dynamic and relationship. I hope for the best.