My bedroom always lets single females in without waiting.

But more seriously, if you want cocktails there's a bunch of places that you wouldn't have much of a problem at, Employees Only in the West Village, Angel's Share in the East Village, Campbell's Apartment in Grand Central. All of those are laid back and chill. If you are looking for something more upbeat like a club, there's Cielo in the Meatpacking which usually has good DJs but there can be a line, Le Bain at the Standard has a great view and is a pretty nice scene. There's a ton of clubs in the Meatpacking District though, so just heading there and finding one that strikes your fancy is probably the best bet.