Our daughter's reports told us that sleep was absolutely fine and not one of the difficulties we might face. And of all the hard stuff, it was sleep that was the biggest!
She was nearly 5 when she came to live with us, and is now 7.
At the very beginning it was fine for a while, and then it descended in a very very long and fraught time of rage, fury and screaming. At one point it was almost as though she couldn't sleep without the storm first. That died down and then she just wouldn't go to sleep for an hour or more. And all the time one of us would have to sit with her. So that was hard.
Even now, 2 and a half years on, it's still unusual for her to go to sleep on her own, without one of us sitting with her, the difference now is that she goes off within a few minutes.
We've tried gradual retreat with absolutely no success!
And I have since learnt that a lot of her friends also have a parent with them while they go to sleep so it isn't out of the norm and it isn't age-inappropriate either.
I'd say if that's what your child needs then just go with it - there's absolutely no virtue in listening to a child getting more and more upset. And there's no law that says she has to go to sleep on her own. If she needs that reassurance then do it.
BUT, make sure you have a smart-phone or a kindle or something because it is as boring as hell! Once I realised I could read on the kindle app on my phone it was fine and I didn't mind sitting with her, but at one point I got more and more resentful and upset, and that was a very ugly feeling to have.