Hi Vera, Do you have a copy of her obituary? Sometimes the Cemetery is listed in the obituary? Also the funeral home is often listed in the obit and they can answer your question along with her parents names, siblings, spouse and children.
If you don't have her obituary, you can support a local genealogy society and contact Seattle Genealogical Society, http://www.rootsweb.ancestry.com/~waseags/http://www.rootsweb.ancestry.com/~waseags/ . They might have cemetery listings too.
You can also order a free obituary by contacting the Washington State Library, http://www.secstate.wa.gov/library/ask.aspxhttp://www.secstate.wa.gov/library/ask.aspx . They will search the newspaper microfilm for 60 minutes at no charge & Email you with what they do or don't find.
I've looked through my list of Seattle Cemeteries and didn't find her name in either list. One large cemetery is Evergreen-Washelli in Seattle, http://www.evergreen-washelli.com/cemetery/index.htmlhttp://www.evergreen-washelli.com/cemetery/index.html . I think they'll tell you if a person is buried there or not. You can also spend $10.00 with them and find out additional info about the deceased person. Successful Searching!