hircine 21 its not a bug. She probably got stung so many times that your 1 stim was like taking a pee in the ocean. They need to let u give them anti venom or they need to use it themselves. I ve had them die almost 1min later, because they only use buffout and think they re cool. When the buffout runs out they just drop dead. Ive pumped 25 stims into followers after they get slapped by cazadors. It would be so much better it they could take antivenom.
There is a bug with companions getting poisoned - if you use a stimpak on them while the poison is still affecting them, it dumps the full load of poison on them at once and often makes them die as a result. This was introduced with one of the recent patches, and hopefully will be fixed on the next patch.
In the meantime, I installed a mod that's supposed to work around this, and also allow them to use antivenom. I haven't had a chance to try it out yet (took a little detour from NV to play the original Fallout), but I'll try it out soon.