>>22
She's very insecure about the relationship, to the point where she doesn't want to burn her chances with the other guys when your relationship ends (yes, when, even though it probably just is an if consciously in her head). After all, she has not met you yet, and most people tend to fear that they've just missunderstood the person they've fallen for online, that they're not like what they seem to be (no, it doesn't take lying, some habits are unnoticable via the intarwebs, some are greatly magnified and others are shrunk down etc - it's easy to get the wrong idea about people). The excessive flirting might be due to craving attention and acknowledgement, and she may be afraid of losing that if the others find out she's taken, and therefor get less interested in flirting with her as she's taken.
I suggest you wait a bit, and see if she feels she is seriously interest in you when you two have finally seen each other face to face, and spent some time together. Some people have difficulties taking online relationships seriously until they actually get physical confirmation for that it's not just yet another dead-end attention-whoring game, the "NPC"s being the people she flirts with. Wait a few weeks after you two have met and once again gotten separated, and then discuss whether your relationship really is solid, or if it is just a pleasant temporary thing.
(Always look on the bright side...)