If your mother won't return the $1,500, you can take her to small claims court and sue her.
As long as you can prove that you were living independently and she was not supporting you, you should easily win in small claims court. This is because if you were living independently and supporting yourself, then you are entitled to take the deduction and your mother is not.
Before going to small claims court, you may want to talk with the IRS. If you explain to the IRS that you were living independently and your mother was not supporting you, then the IRS should go after HER for the money and not you.



