One advice I heard was this: Put two or three nickels just outside her bedroom door. For every time she gets up you take one away. If she stays in bed then in the morning she can have all that are left there. You could use pennies or quarters or whatever.
Personally, I have used the Ferber method and it works for me. Basically, you leave the door cracked but if the child gets up then you have to close the door (stay by it) for one minute. ONce the child quits crying you say, "I will open this door when you have stopped crying and you're in bed." Then leave the door open unless she gets up again, and repeat the process. YOu can stick with one minute closings or increase the time to 2 or 3 minutes. YES the first few nights (maybe even a week or two) is a pain but the kids learn really quickly that if they stay in bed then the door stays open, but if they get up then the door gets closed.
Finally, you could pick a motivation in the morning that she likes, like "watch an extra 15 minutes of TV" or "Get a donut for breakfast" or "Mom will read you a story, just the two of us". Make sure, though, that the reward is for the MORNING because she probably won't remember a reward if it has to wait until later, then the desire for the reward will be gone.
Good luck!