Have a browse thru the Norah Jones, Avril Lavigne, Sheryl Crow, Blondie, Dido, Cranberries, Corrs, Alanis pages on the mainpage www.guitarsongs.info
Just scroll down the artist list on the left, click on the artist to see the songs I have. There should be quite a few you can play, just pick the one you know best, and can play most fluently rather than your favourite... the important thing is to be able to play it easily on the day.
"Strong enough to be my man" is a song everyone knows, has quite easy chords, and a strong female vocal - that's just one suggestion.
