My 3 month old will only sleep 13-13.5 hours every day. That's apparently 2 hours less than average. I know every baby is different but is that too little? If that's not enough, how can I get her to sleep more?

Edit: She's a very happy baby most of the time. If we're lucky she takes two naps during the day. Between 30 minutes and 3 hours, usually one 2 hour late morning nap and one 30 min to an hour afternoon nap. The other hours are in two big chunks at night, separated by just one night feeding.