I used to say sleep time now time to go to sleep, mummy is going to do xyz and I'll come back and check on you in a few mins. If DS shouted I'd go back straight away if no shouting is go back after 20 mins and he'd mostly be asleep. As we got further on with it, I'd shout I'll be there in a min I'm just finishing xyz so time to be quiet and just delay it a few mins.
I think your doing great and if your getting further away its progress and not taking too long. She is feeling secure that your following through what you say you'll do and then it will be easier to accept sleep without u x