EDIT: there is no vet around that will treat her
Edited by PotatoWaffles - 9/24/15 at 2:51pm
Check her mouth right away to see if she has a stinger still stuck in her mouth, usually the tongue or palate. If she does, very gently scrape it off immediately. You can dab some hydrogen peroxide on the sting and even swab her whole mouth with a qtip with hydrogen peroxide.
You can use infant Benadryl for things like this, but it's of course not recommended or covered by the manufacturer. I want to see if @casportpony has any other ideas. You can go ahead and do the things in the first paragraph, but hold off on the Benadryl until we hear back from her in case it's quick. In the meantime, post her weight so we know what dose you'll need.
I'm really sorry, but none of the people I'd otherwise ask are signed into BYC right now. Do you by any chance have any children's Benadry liquid in the house, or can you send someone out to get some very quickly?
In the meantime, if you can get some ice chips on it, that will help with swelling. That's after the stinger is removed.