I have some solo girlsite clients at Sliiing.
The ones that are doing good are the ones that not only do cam shows (cams shows are a must) but they also do nasty hardcore content.
( Gang bang and stuff like that )
I would say that straight solo girlsite are not that successful anymore.
I hope that it will help. it is just my
based on different numbers from my clients. Maybe other webmasters have other experience with it.