I like my best friend?

ive started to like my closest friend that ive known since second grade. ive never thought of her as anything other than a friend for all the years ive known her till now. ever since her now ex bf cheated on her and i spent two staright nights in a row on the phone with her helpin her through everything idk is like i see her in a different way.ive never kept anything like this from her and i want to tell her considering how close of relationship we have but im actually scared ..what do you think i should do