U.S. States: Texas: Bexar County
Have you tried writing for a copy of her death cert. from the State? The cost is $9.00 per copy and if they don't find it, they keep the money. I have found it well worth the money. Sometimes it includes Mother's maiden name and place of birth of both parents.
You can write to Bureau of Vital Statistics, Texas Dept. of Health, P.O. Box 12040, Austin, TX 78711. Then if you get an exact date of death and if it is in San Antonio, contact me and I will look up the obit for you.