There actually is a female liche in my game.
To cut a very lengthy story down to size; Centuries before the current campaign started there was a very bad, very powerful wizard who, along with a council of magi originally convened to govern spellcasters, killed almost all of the world's magic users. After killing the rest of the council, he became a liche to ensure he'd be around to have his way for a long time.
Another wizard and a former member of the council became a liche to ensure she'd be around to stop him. Yeah, she's a good liche.
She also doesn't look like a corpse. Her appearance, while disturbing to anyone who gets a really good look at her, appears to be that of an attractive, middle-aged woman. She's quite pale though, and her skin looks like its stretched a bit too tightly across her cheekbones. She may not look so good after a few more centuries. To her, undeath is a fitting penance for her inability to stop the council leader when she was alive. She views her failure as tantamount to complicity.
She managed to seal him deep beneath the council's underground lair. She keeps watch there now, night and day, to see to it that he doesn't get out.
Her relatively good looking facade is a symbol of her incorruptibility. Well, that and it makes her a more sympathetic figure to the PCs than a hideous walking pile of bones would.

I would have, perhaps, made her a vampire except that it would have been hard to find blood in that underground locale, and I'm not entirely certain there are such things as vampires in my campaign world. She is very, very vaguely inspire by Sethra Lavode
I've never been too happy with D&D's version of the vampire.
Yup, that was the short version.
An even shorter way would be to say, yes, I've got a female liche in my campaign.