S.G.
I agree that she is probably just feeling a little left out right now. We let our oldest (almost 11, also a step-daughter) sleep with us sometimes around that age. As long as you can set boundaries with her and make sure she knows that 'her' room is where she is suppose to sleep, and if you can get her to sleep there the majority of the time, you shouldn't have a problem later. Find an activity you can do with her on a regular basis; a board game or something. I would just make sure to spend a bit of quality "just for her" time each day making her feel special.