Burlesque Sountrack- Who sings that song that is not listed on the cd?

There is one song on the newly released Movie of Burlesque with Cher
and Christina A.
But it is not listed on the dvd or cd.

It is when Christina is visiting the business man's house towards the
end of the movie. She is walking up the stairs and comes upon the
model apartments. It is a woman singing. It is a slow song. I heard
this song years ago and never have been able to figure who it is.
Thanks for your help!