Best I can come up with is either Dariana (already taken by a reasonably famous snek lady) or Darlynn (extra cheesy, reminiscent of a adult-star alias). I humbly request aid and advice from my fellow, ever-gracious Furs ๐
(art is by Blazera, lightly edited from a comm I bought last year)
I see Dariana and all I can think of is Daria, which is a nice name I mostly know from a TV show like 25 years ago with the same title.
I don't know anything about your character but I assume it's purely trying to make Darren sound more fem? If you're hardset on keeping the first couple letters, you'd probably be best off just scrolling baby name sites and seeing if anything clicks, but I'll grab a couple myself: Dailyn, Dalene, Dalenna, Darrelle, Darrellyn, Darylene