What bike for a lady?

Hi folks,
Just wondering what options are out there in regards to ladies bikes?
My girlfriend is 5ft 6inches tall. Looking for something cheep to get started.
I'm not sure what type of bikes are available to suit her.
Any help would be greatly appreciated.

Thank you in advance.
i have a ktm with deore, not a whole lot of use on it, good starter bike
what Muddy Fox said there is 100% correct..too many people buy cheap and then come looking to trade in and up. Mountainbiking is so freaking hard, get the very best bike you can, otherwise its misery, trying it on bikes without air shocks and disc brakes is painful.In fact everybody should be riding mtbs with at least an air shock, shimano disc brakes and tubeless wheels, you are only hurting yourself with anything else and don't cod yourself, Fox or Rockshox , the rest are pretenders..
As a "lady" I agree with Richie, buy the best you can afford as it's hard enough keeping up with the lads never mind if you have a crap bike to contend with as well. God when I think of the cheap(ish) bike I started on its amazing I lasted...
My advice would be to get a hard tail and as Richie said with air shocks and disk brakes at a minimum