Are you trying to say that your best friend is enemy with the one you love? If so, your just afraid of betraying your best friend. If both of your feelings for each other is as strong as you said ,for me as a best friend I would understand and let go of the anger we have hold against each other. Love can't be destroy by others,and no one can stop the flow of water to go the direction they want. Just like the feelings no one can't stop the love between you both. Talked this out with your best friend and explain to him/her how you really feel. I hope your friend support your feelings and I wish you the best.