What steps can I take If my taxes keep being rejected because somebody claimed my daughter without permission

[Anonymous]

your only choice is to mail your return.    the IRS will not accept a second efiled return when someone has already been claimed 

  Eventually the IRS will send both of you a notice asking you to amend.  If no one does,  the IRS will send another notice asking each of you to provide proof.   The one with the better proof gets it and the other gets a tax bill.