Meh, I had my first girlfriend at 19. It's no big deal.

What you have with her won't come twice in a lifetime, you're right... because she's your first girlfriend. That's why this is so special. You are obsessing here, and it's unattractive.

What'd you fight about? It could be that's what's driving you apart, but more likely it's just that what you have is fizzling out. That luvey-duvey big kissy stuff wears out. It wore ME out when I was in my first relationship, and I started as the clingy one.

I know plenty of smart, attractive girls who like video games or like to study or like anime. I also know a lot of smart, attractive girls who don't like study but do like kickboxing, or reading crime fiction, or watching nerdy movies. I know some smart, attractive girls who don't like anime but like performing in amateur theatre. I know some smart, attractive girls who like study and anime but don't like video games. Why the hell should it matter what she likes? Please don't base your future around a girl because you share hobbies.

My guess is that she's sensing how gung-ho you are, sensing how attached to her you're becoming (and possibly sensing the bullshit reasons for this attachment as I have discussed above), and it's beginning to turn her off.