i've been through this. Just a month ago, my best friend's boyfriend broke up w/ my best friend to go out w/ me. my best friend was very sad and said that if he asks me out say no. and that if i say yes, she'll not be my friend or ever talk to me again and will try to break us up. i said yes when he asked me out becuz i liked him ALOT!! i felt that my best friend isnt my best friend nymore for she was telling me what to do and that was wrong. she should have let me decide and not threaten me. so i think if you like him ALOT, then you SHOULD go out w/ him even if ur gonna lose your best friend.