I think my ds was somewhere around a year when he started taking one nap a day (although some days it was still 2). At that time, he was going to bed at 8pm and sleeping for 12 hours. Since he started sleeping through the night, he's been a 11-12 hour a night, kind of guy. He's turning 2 in a couple weeks, and he still sleeps 11-12 hrs, and takes an hour (at least) nap during the day.
Every child is different! I don't think 10 hours at night is too little to be sleeping, especially if your lo is making up for it during the day. She'll probably start only needing one nap in the next few months.
Whiskers