How about Keri Leigh? Or Rory Block? Good blues women. Jazz has a particular difficulty for women in that the older singers from the best years of vocal jazz were so good and so proffessional that they didn't leave much to the younger generations to express. It is really hard to earn a living singing jazz to begin with; then if you choose standards; you are compared to some of the best vocalists that have ever recorded; Ella; Sarah; June Christy; Nina Simone; Abbey Lincoln; Billie Holiday; the list is endless. But there are some good inovative artists that are not boring and can actually sing. Dee Dee Bridgewater; Dianne Schur; Carol Sloane. There is just a few but there are many more. There are so many jazz guitar virtuosos that there must be some you would like if guitar is a personal favorite. Try John Maclauglin's album; Belo Horizonte', it's very mellow and peaceful stuff; not his usual frantic riffs. One of my favorites for late night.