I've run across this name twice in books, not counting "The Help" where it's spelled and pronounced differently.
In "The Last Picture Show" by Larry McMurtry, Abilene is a swaggering, rich, arrogant man about town. It is never clear whether Abilene is his first, last or nick name. The story is set in Texas so it could easily be a nn but it's never specified, he is always just Abilene. I suspect it's just a nn.
In "The Good Brother" by Chris Offutt, a white-supremacist, anti-government woman in Montana has two boys she's named Abilene and Dallas, after the places where their fathers were from.
So the two Abilenes I know of from books were male, but the construction of the name is decidedly female.
I don't like it, it feels too much like a wannabe cowboy nn rather than an actual name.
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin