My 88 year old grandma, has a uti and skin ulcer on her left heal. came down with sepsis yesterday morning. how long do we have with her?

Too little info...: Sepsis is dangerous in anyone, and elderly people are at higher risk for a bad outcome. However, most people recover with aggressive IV antibiotics, proper IV fluids, etc. Her prognosis also depends on her general health. No distant expert can guess at this without a lot more information; you'll need to discuss it with her doctors. Best wishes to her, you, and all your family.

It depends: whether or not antibiotics can pull her through.. Otherwise,if not,about a week or so..