Most likely your return will be rejected, because your SSN is already on Mom's return as a dependent.. Once it does, you can just fix the dependent questions and resubmit.
But first look at your actual Form 1040, and see if the Someone Can Claim You as a Dependent box (tiny print) is checked in the Standard Deduction section towards the top. If so, you already did it correctly.
2020 Form 1040 (irs.gov)
