something like that. If i were in your situation, say I see this chick i'm attracted to in class and we're cordial, then i find out she has a man, personally i don't actively go after chicks that are already taken (partially based on personal moral principle, partially based on the fact that it leaves you very open to play yourself like a sucker). the reason you don't pursue things with her has to be based on something real. it can't be because you're scared. now notice, i'm still polite with her, and if i'm still attracted to her, i don't pretend like i'm not. I don't try to be cooler than cool about it. I keep it real with myself internally. but i respect the fact she has a boyfriend out of principle and don't focus on her so much. this is all internal work but it affects the way you will talk to her and other people as well. your actions will be consistent with your state of mind.
after that, many things could happen. she could start paying less attention to you, she could still be flirting with you, she could confront you about why you're acting different with her, she could ask you if you're feeling her, or maybe she'll start talking about how her and her boyfriend have problems and shyt, or maybe one day she breaks up with him, etc etc etc. you have no control over any of that but the beauty of it is you shouldn't even try to think about it or plan it. you just stay in the right state of mind and relaxed. your actions will be consistent. if she starts asking you questions, be honest with yourself and with her. if yo don't feel comfortable about answering something or about certain subjects let it be known. if she asks you about how you feel about her, be honest but hopefully you're not thirsty. if she starts yapping about her bf and you,re not feeling the convo, cut it short and never pretend like you're interested in what she's saying if you arent.
after that everything that's suppose to happen happens and don't limit yourself to that girl. what you,re saying is right but it has to become like a state of mind to where you don't even have to think about what you,re gonna do or should do.
as far as girls in your city, maybe you give off a different vibe when you're out of town. or maybe girls from yur town aren't as cool in some way. but if you,re not meeting the right chicks, try switching up something. hang out at different places and times with different people. different events, etc. step out of your routine and you'll meet different types of people. but as far as you saying you feel like you're good as you are, confidence is a good thing but always strive to better yourself (again, not for chicks but for yourself). financially, culturally, spiritually, intellectually, physically, style wise, accomplishments wise, etc. you could always be a better person than you are.
I know everything i said seems like a repeat of my previous posts but that's just the way i see the game. some have different approaches though. it's hard to explain in words. it's really about the mindset. you get to that place where you know what you want and you don't let anyone try to force your hand into something else. you're the only one who gets to adjusts your wants and standards. don't let other people force your hand. you keep it real and if she's feeling you like that, she'll find a way to attach herself to you, contribute in meaningful ways to your vision and cooperate. if not, she'll just keep it moving and some other women will gravitate towards you. either way you're good.
EDIT: but if going after chicks with boyfriends doesn't go against your principles, and if it doesn't feel wrong to you, then there's nothing wrong with going after her. don't let anyone (including her) shame you into not going after what you want as long as it doesn't go against your code and principles