hi my youngest gdaughter (2y9months), has decided after months of encouragement she is going to use the potty or loo and wear knickers ! However she is adept at holding on to both pee and pooh and just wont go till she goes to bed and the nappy is back on
It sounds like she wants the comfort of the nappy when she tired and sleepy, and she may be establishing future bowel habits - going just before she goes to bed.
The stickers idea is a great one - little ones love rewards and praise, so heap it on when she gets it right.
If it helps, check out your local primary school - no children there in nappies - they do all get there in the end!
She will still have the comfort of a nappy, but at the same time she will learn what it's like to be "wet" and that it's not a nice feeling. Hopefully it will encourage her to use the potty instead.
Does she sit on the potty in the daytime and not do anything? If she does, then from what you have said, it kind of sounds to me like she is feeling the pressure of the "encouragement" and this is her way of dealing with it, but really she doesn't feel ready to use a potty.