Darla is femiinne, but classy? Hardly. It is not considered to be a classy name by most people.
I find it middle-aged and trailer-trashy, like a waitress with bleached-blonde hair and too-tight clothes, chain smoking and trying to pick up her diner customers.
I've also often had my own name misheard as Darl when I answered the phone at work with "...This is Starla."
Darlene is some better, but I'm not fond of it. As far as arl names for girls go, I do like Marlena or Marlene, and Charlene, which is my MIL's name. Also Carla is kind of cute.