I'm hearing you I am going through exactly the same thing atm. DS is the same age as your DD and we have good days and bad. Some days he wants a nappy but will sometimes still tell us if he needs to go wee or poo. Other days he will want big boy undies (the terry towelling ones with the plastic inner so they don't leak through) and will tell us when he needs to go. It is still not a 100% success rate. And although sometimes it is extreamly frustrating - like when he goes backwards and forwards to the loo 5 times with no result but the sixth to do a poo, i keep reminding myself he is only learning and even if it interups me or i need to clean up where his wee has gone on the floor as his doodle was not aimed properly into the potty not to push the point. I am in no rush, and judging by DS neither is he. With the warmer weather upon us and being outside alot more DS has also in the last few days taken joy in weeing on the grass- propbably not possible for your DD. My suggestion is to just go with the flow. Either persevere at where you are at or give it a few weeks and try introducing it again. My experience from DS#1 was that the more i tried to push the further he would run away from it. When he did start we were done in less than a week except for o/night.
Maybe try a star chart, and everytime she tries to sit on potty she gets a star/stamp and when she is succesful she gets 2, or gets a small treat. My Ds loves the idea of being able to flush the toilet after he does a wee or poo when he is succesful.
Good Luck