If you told your best friend you liked a guy and you told her not to tell him and she told him should you be mad at her?

Yes. As she is your best friend an she told your secret!

(another person):well think abotu it if she is truly your best friend and you think you should be go a head but is it really worth loosing your best friend over one little thing that doesn't really matter because he was bound to find out eventualy even if your friend hadn't told him