So sometimes kids don't potty train until they are ready. Regardless of how badly parents, and day care teachers want it.
My daughter started to potty on her own at 16 mths old. But she didn't potty consistently (meaning all the time without a pullup) until she was past 3 yrs old.
I know it seems crazy. What worked? We were at a friends house playing dominos. She comes to me crying because she had a poopoo in her pullup. I said ok, and went to change her. I asked why she was crying. She said because the other kids made fun of her and called her a baby for pooping her pants. It was at that moment she told me "Mommy tomorrow I wear panties". I said ok baby. Just thinking it would be the same old thing with her. It wasn't. SHe literally start wearing panties the next day and kept on going potty just like she said.
It was peer pressure that got her to understand how important going potty was.
Now my youngest boy on the other hand.. well.. mawmaw and pawpaw turned him loose naked on their land and he potty trained himself once he knew where things were coming from.
It took 3 days.
The important thing to remember is that every child is different. If she understands potty and just hasn't made up her mind yet, I would suggest talking to your pediatrician to see if they have any creative ideas that other mom's have used in the past.