Bed time

So long story short i married this wonderful man who has a 3 year old daughter. Her mother is not in the picture so it’s been him and her there whole life. His parents spoil her beyond belief cause they don’t like to “hear her cry”. Now my problem is she will not sleep by her self under any circumstances because she has always slept with someone. I’ve tried laying with her till she falls asleep, bribing her everything she still cry’s and says she wants to go to mom moms. What do we do and will she grow out of this😩