I know a whole lot of girls named
Ashley. Most of them are
Ashley, although I have met the occasional
Ashlee,
Ashlea, or
Ashleigh. I don't know any Ashleys older than 30 but the rest are almost any age below that. None of them go by a nicname.
Ashlyn is okay, maybe, but I don't like Ashby. I've never met any Ashbys, so it's probably safe from overpopularity, but I still don't like it.