I'm no expert, but if you can help her through this now she'll be better off in years to come. Maybe she thinks that something bad that once happened could have been prevented "if only she had...(fill in the blank)". Try to figure out what that was. Explain to her that it might seem that she has that amount of influence but sometimes 2 things happen at once but don't seem related. Use an example. Do not try to prove that they are not causing each other, just show that there is the least amount of things in common between the 2 things occuring. Confusing? Pick an example of something steady and something changing. Sometimes they occur at the same time but other times they don't, the 2 things don't automatically happen in tandum. Make sense? I hope so.
Sometimes when kids are young, it's typical for them to not understand about other how other people experience things just as they do and how that child is not the only one in a made-up world. It may take time for your daughter to learn that she cannot control the things that happen merely by turning on and off the faucet 3 times.
Another idea is for you to role-play what you want her to do. Have another adult outside the house help you. Phone them in front of your daughter. Arrange things ahead of time and then while on the phone in front of her, openly ask when they'll call again that day. "you don't know?", you ask. "ok, we'll be here."Hang up.
Use that event, the randomness of when they'll call, and one of the habits she does. Have the person call once after you imitate the habit, then have them call at a different time, much sooner or much later than before when you do the preferred habit. Do it again, but slightly differently the next day. Try to show as little in common between the call time and the habit you're correcting... then talk about her habit not controlling the weather or the number of cars going by in an hour or the number of times the neighborhood dog barks. Don't tell her it's silly or she may feel she's failed in drawing conclusions. Just ask her "is it more likely that you turning the water on made the dog bark or that the person passing the dog made him excited?" If your daughter is old enough, she may understand, if not, this looks more like what I did when we had no routine in my home and I desperately wanted predictability in my life, like someone telling me what when bedtime was approaching so I could have time to react and not feel caught off-guard. I used to flick the light switches on and off an even number of times when I was 5 because I'd seen some people be supersticious, doing weird things. But I stopped when it seemed to have no effect on goings-on. Good luck.
-Kris