Hey people what do you think of this when a girl you like does this and she doesnt know you like her?

well hey people what up i am brandon i am 6'7 and 16 and i like this girl in my 2nd block her name is brandy and i have not really talk to her alot until today.I was abest for a few days then asked her what we did we started to talk and then like 5 minutes later this guy came in and just said her full name that was right before i asked her i she wanted to be my partner for a project she had said no that she didnt have a partner and then i asked her if she would like to be partners and she said yes then right after that i left for like two minutes and next thing i kow she is with this other guy the same guy who was still jsut saying her name.I dont know what this means and well i talked to her does this mean that she just wanted differnet partners or does she not like me please help.I dont know if it has anything to do with it but she is only like 5'4 and i am white but i think i am pretty good looking and she is black and the other guy was black to is that what was wrong please help?