She has learned habits that don't serve her well, and now you'll have to re-teach her. Expect that this will take a while. She's had years of doing otherwise. Bite the bullet and be firm about what's expected. If you waver, you will be doing this for years.
Has always stayed up late but sleeping on her own is a new thing, she used to sleep with me and now need to transition her to sleep in her own room?
When you mention that she just recently started sleeping in her own room, how did this come to be? In other words, is this sleep issue a chronic problem or one of acute onset?