have you been clicking that checkmark saying 'I can be claimed by someone else' on your prior tax returns? if yes, why? if no, that is fine.
when you file your 2020 tax return, there is a 'settle up' section for the stimulus. The money you are due will show up on Line 30.
ps - your mother did not get your first stimulus check in the amount of $500 (you are not suggesting she cashed a check made out to you, right?) . Dependents over the age of 16 are not eligible.
