A.W.
I personally would let her sleep with me. What harm is it going to cause. You could get a good night rest and so can she. Her life sounds pretty traumatic. She will out grow this wanting to sleep with you, but why the concern her sleeping with you? She just needs her security.
My children slept with me most nights if they wanted to and did not hurt them. They grew up healthy and stable, and independant. Now having families of their own.
In the 60 and back families doubled up in rooms and beds and children slept with parents they did not have multi room homes. And they grew up healthy happy socially rounded. What is the issue.