Oklahoma doesn't publish any of their vital record dates which makes finding death info more difficult. You have to look up dates in cemeteries, obituaries, funeral homes, etc. Also sometimes when people divorced, they told the Census taker they were a widow/widower.
She wasn't listed in the obituaries that are on-line but that listing is a small part of the total.
The Northwest Oklahoma Genealogical Society, www.rootsweb.ancestry.com/~oknwgs/ has obituaries too.
The Dewey County Court Clker has divorce records starting in 1894.
If she died 1908 or later, you can request a copy of her death certificate from Oklahoma State Dept Health, www.ok.gov/health/Birth_and_Death_Certificates/ but they have a lot of restrictions. Successful Searching!