I said that I could not be claimed as a dependent when in fact I could have been claimed by my mother
You need to mail in an amended return. https://ttlc.intuit.com/replies/5567856Did your mother's return reject? She will have to mail her return this year.
How would I go about changing that even though I already received my refund?
She still has yet to file... she informed me of that yesterday
She still has yet to file
Tell her she will have to mail her return this year. If she efiles it will reject for dup ssn since your ssn has already been used.