My mother wants to claim me on her taxes this year but she can’t because i already put my tax order in, how do i cancel my tax order?

If the IRS accepted your tax return, you will have to prepare, print, sign and mail an amended return to change your return to say that you can be claimed by someone else.  DON'T change your return until you start the amended return. WAIT until you receive your refund before starting the amended return. Here is how to amend a return: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed

Your mother can go ahead and claim you before you amend your return but she will have to print, sign and mail her return to get it accepted. She would have to do this even after you amend your return because it takes many months for the IRS to make the database correction for a dependent change.