if it is dry also try vasoleine.(sp?) it will help heal and keep moist. put on after you alco wipe it.

has teh dr given you any antibiotics???

is she a chucky baby? she may have an infection in her tummy causing the thrush and slow healing of her belly button?
have they done a swab of her belly button to see if any nasty's are growing?
i woudl ask for a wound swab and some antibiotics as her body is able to fight this yet and its going on to long