What does it mean?

So my friend said this one girl liked me. She was one of the most adored girls in the WHOLE grade. I'd already known her for 7 years so this information coming to me was a shock. So, i asked him multiple times "are u sure??" He seemed completely honest. "Seemed". Then the next 2 months i try talking to her more and making friends with her. It seemed to work pretty good. "Seemed". I asked ALL my friends about how to check if a girl likes you. I took their advice and used them on the girl. They seemed to work good. "Seemed". As i was doing this, i started to develop feelings for her. Not long after i told her i liked her, Her face instantly turned SUPER RED and blushy. It seemed she would tell me she liked me too. "Seemed". She said she didn't like me back.... and i felt crushed. I told her my friend told me you liked me and she said "Well hes a liar..." It seemed like the worst situation ever. I embarrassed myself almost in front of the entire class!! But she kept quiet (Thank god). I asked my friend "WHY DA FU** U LIED TO ME???" he replies "Dude, i said i was kidding.." All my friends stayed on my side and said he was SURE she liked me. He then says "I was testing my lying ability." That was the also the very first day i cussed publicly and on purpose. I was just SO mad at him. Ever since, that girl has hated MY GUTS. She will frown every time i talk, not laugh at the jokes she would laugh at, and go out of her way just to not talk to me and/or ignore me. Why? What does it mean?? PLZ HELP MEE!!!!