About the same size as you and have bikes in varying sizes from 16 to 20" seat tube lengths. Depends on a few things like, the geometry of the bike, it's intended use, what you like. I like my hard tails on the smaller side, FS and road bikes bigger but again, it depends on the bikes geometry. My 5'4" wife's ht Cannondale is the same seat tube length as my ht Jamis, both xc, same year, with just about the same size stem, yet her bike fits her well and is too cramped for me even if I move the saddle. Since you're a self proclaimed "newbie", and are asking, so you don't know what you like or want, you should just get fitted at LBS, and go with that, unless you don't trust them then you should go some where else right from the get-go. To some extent you'll get used to what you get, if within range, and that'll be, most likely, what you learn to like. It's not unusual to cut the seatpost for a proper fit if the seat post is stupid long. You can also adjust the for/aft of the saddle, as well as the up/down, and turning the handle bars will increase/decrease cockpit size if they're riser bars. If a bike is close to feeling comfy, after making those previously mentioned adjustments, try to get the shop to change the stem to one better for you for the same price and keep the old one incase you change your mind once you ride a bit. Think when you first start riding, you'll wanna be more upright and looking forward, and once you get into better mtb shape and more skilled, you'll wanna be lower and more aggresive.
My .02, Oh and welcome to the site!