Should I tell her? (I need more answers and soon)?

Ok so im a girl... I want to tell my bestfriend (whose a girl) that I love her... Like, I would do anything for her, and I trust her with my whole life but at the same time IM not lesbian an that I just want to do anything for her and that I would stop what ever the hell im doing just for her and i dont even know how I feel in a way... Like my heart aches without her but the thing is... she has a boyfriend who she cares a lot for she even tells me her secrets but i dont even know... Im not sexually attracted to her either im just personality attracted? Im afriad that if I do tell her this stuff that she wont want to be my friend and we will slowly stop becoming friends and truth it id rather not tell her at all then stop becoming friends with her because i seriously deeply love her... but i want to tell her cause it hurts me inside... How should I word it? i dont even know...

Im not lesbian either, im attracted to guys but..

Also i have told her that she truly is my best friend, but I still feel this thing in my heart for her it seems like its not enough...