How is she waking up? Upset or groggy? Hungry or hurting? I know that with my two kids, when their sleep changed I could attribute it to either new stage of development or a physical thing that was waking them up. Could she be teething? Molars, maybe? My two would be miserable with them, and they take SO LONG to even break the skin! My daughter had ALL of her two year molars at 14 months, so don't think it is too early! I would give them a little baby motrin or tylenol (whatever works for yours), right before napping, then as I put them down, a teething tablet or a swipe of oragel. With both, you are easing the short term pain (teething tablets or oragel) and the long term pain (tylenol), whichs help them sleep longer, because they aren't hurting so much so soon. And the oragel/teething tablet/tylenol don't interact....Hope this helps! These little ones always keep us guessing! :) Have a great day!
P.S. Have you tried seeing if she will sooth herself back to sleep? She might just be experimenting with you...who knows!?