Is it bad to fall in love with your best friend?

well its quite a confusin situation, ive been best mates with this girl through out high school, we're like brother and sister we laugh at each other all the time n its great but at the time i just saw her as a mate n i never saw in ';that'; way. I knew she liked me more than a mate but i just ignored it everytime the topic came n eventually i think she just gave up but we stayed the same. She then hooked me up with her mate which was abit of fun at the time n also she met this lad. School had just finished n we said our goodbyes n that n i felt sick deep inside that i wasnt goin to see her everyday i think thats when i started to realize how much she does mean to me. we started different colleges (near to each other) n we now and again bumped into each other if we were on the same bus at the same time n it sunk me each time i dint get to see her. I missed her sooo much n coz i was goin out with her mate i was always tryin to include her in with what we were doin which lookin back seems quite stupid lol but it was her i was wantin to see badly. In the end it got to stage where i felt i couldnt treat her mate the way i had been like lying to her sayin i love her and gettin serious with her so i called it a day with her n made a silly excuse about her not being right for me. My best mate is still with her bf but he dunt treat her right she's cried so many tears over him but she wont stand upto him coz she is scared coz its her first proper relationship n she dunt want to be on her own. I dont want to ruin things between us and i dont wanna be the reason they break up but i dont think i'll find anyone who's like her. do u think i should just leave things n let them be? or should i tell her how i feel n hope she still has feelins for me?n what should i tell her? sorry i writ an essay btw lol, cheers mikeyIs it bad to fall in love with your best friend?
tell her how you feel. and say what you told us.