Clair, we are on night 1 for the big boy bed for Aiden... so it is new for us, but we have this plan in place.
* If he comes out, we walk him back in & tell him it's nighty-night time & we plan to do that for as long as it take be it 100 times (yuck)
* when we put him in the bed, we put his big puppy dog in the bed under the covers & told him he had to make sure that "woo-woo" didn't jump out... he hasn't come out & it is over an hour.
* we have a lamp on a timer set to go off at a time we have decided is acceptable for him to get out of bed - 6.45, which we will slowly move to 7am, but the last week he has been awake just about 6.40, so we thought that was best. So if he comes into our room before that we will explain he can come in once the light has gone on.
He has had naps on a mattress for a few weeks & they started short, but today was 3 hours! Admittedly Aiden mostly asks to have a "rest" for his midday nap & goes straight off, but he knows he gets his dummy so that helps 7 he has been going to bed well for ages now, but a few night wakings, so we have that to see.
what ever you do be consistent & try as hard as you can not to get angry, but just matter of fact, if she gets a reaction even if it is negative, she will repeat, remember she is still dealing with the issue of sharing her mum & a negative response is better than none at all. so you have to try & get as close to none at all.
Maybe also try an extra couple of stories or longer cuddle at bed time.
Another thought, I have been making little books (pictures) for Aiden, to deal with changing rooms at childcare & giving up his dummy, so maybe make a little book to read (not at nap time) about a little girl named Ruby, who made her mummy & daddy so happy, because she stayed in her bed & slept all night long.