what mtb for a beginner who is short?

[Irulan]

Well, you won't ruin the bike. That was a really lame thing to say. And, if you never bother to learn any MTB skills, (clinics etc) learning on a FS can make you a lazy rider, but that doesn't mean you shouldn't do it. You should just be aware that it takes a little more effort to learn to use your full body as its own suspension in concert with the bikes suspension.

MTBR.com's Women's Lounge has some really excellent, extensive threads on bikes for small women. You might pop in there and read up on more options.

I just helped a friend who is 5-2" pick out a bike. Really I just hung out while she test rode. You need to make sure that you have enough stand over room, and that the cockpit isn't too long. You will understand this by trying several bikes.