DGS is 9 and until a few months ago ended each night in his parents bed with his mother, while his father moved into his bed. He would also not sleep anywhere, not even at his grandparents, unless he had a parent with him, so he had done no sleepovers, no camping nothing.
His parents (and his grandparents) were relaxed about it, constantly encouraged him to stay in his bedroom. He was told he couldn't sleep on the top bunk of his bunk beds until he stayed in it all night, so he has quite happliy slept on the bottom bunk. We knew the time would come when he was ready to sleep all night in his own bed and it did
At the beginning of July, just after his 9th birthday he asked if he could have a sleepover with a friend, which he did. A few weeks later he stopped moving into his parents bed and is now proudly esconced on the top bunk. He has now been on several sleepovers and sometime soon he is going to stay overnight with us.
The moral of the story is that children differ and some child has to be at the extreme end of any distribution. Your DGD will reach a point when she feels confident and ready to sleep without a parent. For us DGS was 9 before he reached that point. But eventually he got there and I think he is more confident and happy because, although he was constantly encouraged, no pressure was put on him and when the time came he just did it on his own.