I didn't see her either. Apparently she was one of the crew members in the helicopters at the end but we never saw her face. Very strange set up if you ask me. I thought the whole point of seeing her was to set up the next film?
It uses the mind control gem from the 5th game but iumbrella/Wesker wouldn't have any reason to mind control jill in the film series.
The 3rd film was probably a mistake as it moved the films away from the videogames 'real world sertting with contained zombie outbreaks to an after the end Mad Max setting that was even more unbelievable and played completely straight.
I thought it was actually a very clever reveal of Jill, showing her name in the ending credits before she actually appeared. Same as the ending of Metal Gear Solid 4:
Big Bosses name interrupting the fake credits sequence