even if you tell her that while she is at daddies she doesnt need to wear a nappy because she can go to the toilet....(that way she will know that even if mum puts her back in nappies at daddies she goes to the toilet)
but your doing a great job and accidents will still happen and by just saying opps we missed that one but next time you feel you need to poo come and tell us and we cant take you to the toilet.
HTH