Lol -- we have a LOUD, LOUD, LOUD cat who loves to yowl at us all night long, so we have tried a lot of things.
The best advice I can give you is that you need to stop getting up and feeding/petting her. I know it seems like a good idea, but it's really what got you into this situation to begin with ... believe me ... that's why our little Opera Singer developed the issue in the first place.
Cats are very very smart and very manipulative. If they figured out that they cried once and you got up, then they try it a few more times and see what happens. If you get up every time, then they take advantage of the situation and start doing it constantly
For our guy, we realized after a while that it wasn't really the food or anything concrete that he needed -- it was the company. Most cats are very social and they get bored being by themselves all night when you sleep -- they figure it'll be fun if they wake you up! Makes sense ... lol.
Basically, there are two things we started doing that (mostly) got rid of his problem. First, we feed him a big, delicious meal right before we go to bed -- the fancy kind of wet cat food. He gobbles it up and stays happier and more satisfied during the night. Even if you only feed dry now, I'd consider starting some wet food at night because a) it's better for them than dry food and b) they are such pigs that they will gobble it all up and get full vs. dry cat food which is not so delicious and which they just nibble on.
Second, squirt guns

... get a bunch and fill 'em up. Every time she yowls during the night, squirt her. Every single time. Consistency is really important. I'm not sure what you should do if you shut her out of the room. You could just get up and squirt her each time -- don't worry, it should only take a week or two if you're consistent.
A final suggestion -- make sure she has some toys she can play with by herself like "doorway jumpers", catnip mice, those round thingamagigs with a ball that goes around and around in a circle, etc. That will hlep keep her busy and less bored during the night.
Our kitty is much better now, but he still has his moments. We find that if we go away on a trip, the yowling will start up again for a while when we come back. I think it's because he has been so bored and lonely and gets a bit anxious at night because he's not getting attention.