Shiny, a 160 might take some getting used to, but believe me, it's a fine size. Ski shops will tell you otherwise, but you'll be fine. I'm 5'3'', 105lbs or so and I'm on a 163, and probably would have gone for a 168 if I found that one in the shops.
Also, don't buy into the junk that you can't ski on a ''guy's ski''. most every girl skiing park right now is using a guys ski, and they don't seem to have much problem. It would be rediculous if there was. A women's ski might have different flax patterns or different core or whatever, but in reality aren't much different than the guy's models.