G.♣.
Here's what I did, and it worked (took about 10 days?):
I sat in my son's room (with my book on my ipad) and waited for him to fall asleep. I did that for a couple of nights. That way, if he started to even think about getting out of bed, I reminded him that it was bedtime and to go to sleep. If you are in another room and your daughter has to get out of bed, she's already waking up a bit more and has to relax again when she gets back to her bed.
After 3 or 4 nights (and him not really trying to get up anymore), I made an excuse to leave the room with the promise of coming "right back." "I'm going to start a load of laundry, but then I'm going to come right back." I always came back! Each night, I stretched out the time until I was coming back after he fell asleep.
One of the reasons kids get up is because they think there's something exciting going on while they are asleep. If you sit there very quietly, you're not out there somewhere having a party without her, and she can relax and go to sleep.
I don't see why you need to lock her in her room. Help her fall asleep.