Ani DiFranco has recorded with Utah Phillips, and Dar Williams has toured with Joan Baez, which assigns these two SINGER-SONGWRITERS sort of fringe-folk credentials. Holly Near might also qualify, but the rest of the performers mentioned are clearly pop/rock/SS, whereas Melissa Etheridge is (IMO) just crap. It appears to me that "womyn's music" as a subgroup of American popular music tends to value sexual identity over quality.

Cheers,
Michael