Although we don't allow the kids in our bed, we still had the problem of our child getting up in the middle of the night and not wanting to go back to bed. I established a "treasure chest," filled with cheap toys and trinkets from Oriental Trading/Dollar Store/Target's $ Bin, etc. We established the rules...if you stay in bed for the entire night and do not disturb/wake anyone, you get to select a toy from the treasure chest in the morning. (It should go without saying that our children are absolutely allowed to get out of bed for real needs, such as bathroom, illness, fear of thunder, etc.)
For us, all it took was ONE night of his sister picking a toy from the treasure chest and him missing out...from then on he stayed in bed!! After about 1-2 months, we simply stopped using the treasure chest. The excitement over the trinkets had diminished and he was staying in bed every single night. It was absolutely worth the small expense!
I doubt this will work if you allow her to get in bed and cuddle with you some of the time, but not at other times -- that would be difficult for a child to figure out. No matter what you do, I think you'll need to establish a hard-and-fast rule she is able to understand.