We are so sorry to hear about your loss. You came to the right place and are here to help.
Before you file your mother's return, make sure the Social Security Administration has been notified of the taxpayer's death. You can either go to their website or call 1-800-772-1213.
Many (but not all) states allow decedent tax returns to be e-filed as well. We'll let you know when you get ready to e-file the state return.
You can sign in using your own account since you are filing on your mother's behalf.