I just noticed a couple of sentences in the "personal life" section claiming that Nicks has said she is bisexual. In this interview.
Windy City Times News Archive - Stevie Nicks: Rock legend on gays, Glee Celebrating 30 Years of Gay Lesbian Bisexual and Trans News.
Stevie Nicks: Yeah, and if the book were to come out, a lot of people would cease to think of me as this eccentric, flaky girl. But truthfully--no, I'm not bisexual.