The piece of paper she needs to sign is the one which makes the car entirely your property, not hers. In some states that starts with her signing over the title, and your taking that to the DMV to have a new title issued in your own name; other states may handle this differently.

You then need to to whatever else your state requires of someone who has just purchased or been gifted a car.

If she gets her finances in order quickly enough, you can then sell or gift it back to her the same way. If you don't think that will happen, sell the car and if you're feeling kind return whatever payments she made on it.

... As has been said in many other answers, never co-sign anything unless you would be willing to loan them the same amount -- because if anything goes wrong, that's what it turns into.

The piece of paper she needs to sign is the one which makes the car entirely your property, not hers. In some states that starts with her signing over the title, and your taking that to the DMV to have a new title issued in your own name; other states may handle this differently.

You then need to do whatever else your state requires of someone who has just purchased or been gifted a car.

If she gets her finances in order quickly enough, you can then sell or gift it back to her the same way. If you don't think that will happen, sell the car and if you're feeling kind return whatever payments she made on it.

... As has been said in many other answers, never co-sign anything unless you would be willing to loan them the same amount -- because if anything goes wrong, that's what it turns into.