Try looking on https://www.familysearch.org/ . This is a free search site and they have the Social Security Death Index. You may find you Aunt listed there or if you know the state she lived in you could check their goverment site and may be able to view a death certificate. Once you know the date she died and where you can look online for newspaper or online obituaries (or you can look without these details-by googling her name-you may get lucky).
You can send a private message to the profile manager for your aunt on her profile page. If you need an invitation to join, you can ask that profile manager to invite you. Or, you can go to the page of people willing to invite new members.