Emily, I'm no MTB expert, but I do have a a Cane Creek Thudbuster LT SS on my hardtail. It's one of the better reviewed suspension seatposts on the market and it's set up so that you use different elastomer combinations based on the rider's weight. If you go this route and if memory serves, you'll have to seperately order an extra "white" elastomer because of your low weight. You'll also want to check the specs on it, or any SS that you order, to make sure you have enough clearance for it. Your seat has to be high enough so that's there's room to accommodate it.