She obviously knows the concept of sitting on the toilet when she has the urge. She will get the hang of it eventually. Just hang in there

I agree with the previous poster. I am going to hate myself for saying this but when you hit a wall sometimes bribery is the only option. When she gets the toilet right give her a small lolly. Only do this for a few days until it works then wean off the lollies. Please don't jump on me everyone, it is just when all else fails