Good for her!!! If she is going on her own and you are not forcing it, then she is ready. My oldest was completely potty trained by sixteen months, and she doesn't have any problems. I did what you've been doing, sitting her on the potty since she could sit up. My second was a little slower, but was still potty trained by twenty two months. My daughters both showed signs of knowing what they were doing at an early age, and I just followed their clues. I think we as parents sometimes ignore the signs are children are giving us, and then when we are ready, they are confused because they were ready before we thought it was time, and we continued it. My son, is eight months old, and at six months old he would take his pacifyer out of his mouth and drop it. Everytime I put it in his mouth he did that, so I quit giving it to him because he no longer wanted it. I think your little girl is smart, you have been training her without forcing so she is doing what has been taught. Keep up your routine.