You got some good advice already - but the one thing I didn't see is that sometimes, she will still need the two naps and sometimes she'll be fine with one nap.
My dgtr transitioned from 2-1 nap around 12-14 mos. So, it's not early at all - she's just who she is and she might be ready. On the days when she is good or only somewhat tired - keep her occupied with play or find a quiet moment, and move her afternoon (well, only nap ) time earlier to right after lunch or something like that. If she's really exhausted - give her the am nap and keep the pm one at the original time.
My dgtr always took a great nap in the am (1 1/2 hours), and rarely napped great in the afternoon anyway (45 min, maybe 1 hr if we were lucky). The afternoon one is the one she started to drop. When she was on the go in the am, I put her down around 11:30 (she never napped longer than 1 1/2 hours at a time, even with one nap!!) and moved it to after lunch as she was more consistent with it. When she'd go down at 11:30, we ate lunch after her nap around 1 or 1:30. If she was really tired (usually happened every 3-4 days or so) in the morning, I would still lay her down around 9:30, 10 or so and again in the afternoon. Since her morning nap was always the guaranteed one, and that's the one we moved to a little later, it wasn't a terribly long transition - maybe 3 weeks total.
So - find your groove, and her groove and she'll soon be on one nap I'm sure - it sounds as if she's ready. Everyday may be a little different - some days quiet time will do it and others more active play will be needed to get through the 'slump'!