Just giving my .02. Im 28 now and have been through this my fair share of times. You always want to be a good guy and be nice to your girl, but there def is a line. Speaking from experience, you cant be too nice and bend over backwards for her when shes acting like a brat. When my relationships have gotten to this point, the outcome has always been better when I say enough is enough and stand up for myself. If there is another dude shes flirting with, sometimes its best to say 'seems like you need time to get your head straight, call me when you figure things out. But im not gonna be sitting by the phone in the mean time.' Then stand your ground, dont call her. We all know the saying: absense makes the heart grow fonder.
Regardless if they'll admit it or not, girls always need a challange. Even in long relationships. Once you become too nice and do whatever it takes to keep em happy, they can start to feel that they can do anything and walk all over you. But once they know there is a line and once they cross it they'r in deep s*** they'll look at you in a whole different light.
Now Im not advocating turning into a dickhead and becoming manipulative, but stand up for yourself and make it known that you have no interest in being in a relationship with a spoiled little drama queen.
For me, knowing my girl is openly flirting with other people is a dealbreaker. Its seriously the second step in becoming a full clown cheater (the first one is thinking about it...) It shows she is testing the waters and wondering exactly how green the grass is on the other side of the fence.
You also said something about not talking to any other females (even platonically) so as to aviod other relationship drama. Reading between the lines it sounds like your girl has given you a fair amount of s*** in the past for it? In my opinion and in past experience, the girls that get insecure about this have larger issues. She should trust that she has your love so on lockdown that you'll never be tempted by other females in your life. She might also be attempting to keep your female interactions to a minimum so that when she does stray or semi-stray, you dont have any options and will be more likely to forgive/ try to forget.
Hope this helped.