I'm gonna give it to you straight, friend, because I've seen all kinds of women in my 51 years and this is exactly why you don't date seriously "9's" and "10's". Unless you're prepared to be hurt or shared with others, because this is how they act. Why? Because they can. Hot women get attention, there's no way around it. And the hotter they are, the more guys want in her vagina. And she loves the attention, never forget that. You are dating the exact opposite of who you should be with. You want Tina Fey...not Farrah Fawcett in her prime!
I always tell guys who are dating hot women to just keep the jealousy intact, on hold, and don't let your inner emotion for the woman get out of control...or she will control you! It's always best to keep emotions tempered and enjoy the moment with her. The sex is great, you're into it, she's into it, you enjoy the pride of a babe on your arm when you walk around town...that's the upside. Enjoy the upside. You're completely normal in how you're thinking right now but...so is the hot babe. And you said it: you're the introvert and she's the extrovert. You'll never change her so don't even try.
I recommend to have as much fun with this honey as long as humanly possible, learn a few tricks, then concentrate on "Tina Fey". A woman who looks pretty and has an awesome personality and meaning to her life. Every guy should have the good fortune as you do right now to be with a "9". Enjoy it for what it is. Who gives a damn if she's been to dinner with others...she's temporary, friend, and never forget that. Go get her, Tiger!