I am a WarmShowers host, as both a single woman and now as part of a couple. I try to be especially welcoming to solo women travelers! I don't get a lot, but those that have stayed have had many positive experiences. WarmShowers provides the ability to leave feedback (both for guests and hosts) so pay attention to the feedback. Contact hosts several days in advance by enpmail, and try to have at least one phone conversation. Trust your instincts. And have a great time!