hiya
i wouldnt worry too much, it depends on each individual child, i have 2 children, my first was in pull ups till about 5 or 6 my second never needed them!! she was really good never once wet the bed till this day,
give her her last drink for the day about 1-2 hours before bed time and take her to the toilet or potty before bed.
you can buy those waterproof sheets for the bed just incase of accidents,
try bigging it up that she is a really big and clever girl with no nappy and tell her how grown up she is! and slowly day by day reduce it.