N.W.
You could try ignoring her. My DD does things as long as they cause a reaction, and it doesn't matter if it's a negative reaction. She's trying to get SOME reaction out of you!
I'd say on the weekend if she comes in to wake you up, ignore her. Pretend you're sleeping no matter what she does. If she screams and wakes the other one up, go and comfort the other one back to sleep and ignore the 4-year old. Let her sit, let her scream, let her do whatever. If she tries to do something harmful, take whatever it is away, but do it emotionlessly and don't say anything.
Not getting a reaction may make her "turn up" the drama, but then you know it's working. She's trying to see how much drama she can stir up. If you give her no reaction, she'll turn it up until she decides it's just not going to work. When she calms down again, tell her gently "it's bed time" and then take her back to bed, saying nothing about her "drama."
You might not get sleep that night, but it should work.
When we can't seem to "punish" bad behavior out, or encourage it out with positive reinforcement we use the ignore method and it works every time! Both methods put attention on the behavior, either attention on doing it (with punishment) or attention on not doing it with rewards. The ignore method does neither, and it's true that if you ignore it long enough it will go away (just make sure you really DO ignore it, and it might take a night or two but it will be a permanent fix!)