L.S.
This happened at my house too.. when they realize that potty training is more work for them, and it is easier for Mommy to change them. NO MORE DIAPERS!! Gone, get them all out of the house, and announce it. There is no options.. TOILET only! This worked for us.. any going back and forth just confused my son, and after I did this, he fussed for one day, and then was perfect..the occasional accident, but it worked! And if you have to use pull ups..and don't want her thinking that they are 'diapers' name them something else..like night time underwear, or order some cloth pull ups, they look like undies, but can be washed etc. On Cottonbabies.com or any cloth diapering website. Good luck!