ive been gaming my next door neighbor for about a week, we talk and have fun, i tease her im c & f and i neg her and i thought it was going good cuz she was laughing and introducing me to her friends, saying hi to me in school and saying hi to me as i walked by her house but now its like shes cold all of a sudden, whenever she looks at me and we make eye contact she breaks it off quick, and whenever we talk online she seems serious and brings up her boyfriend even though when we were having fun she never bought up the fact that she had a boyfriend (which i knew before i started gaming her), and finishes the conversation quickly why is this, im not needy, or creepy with her, is it because shes genuinely annoyed by me or is this sexual tension?

If I were to guess I would say her girlfriends got to her. They were probably ragging on her for her flirtations with you and she became more aware of what she was doing and got a little bit freaked out. But no worries just keep acting c & f and don't change a thing regarding how you act. Keep building that comfort and show her that when she mentions her bf it doesn't change how you act...this will allow you to more effectively game her