IMHO

it is never fair to allow any potential partner male or female to believe I am interested on a sexual level when I know better. If she is your real friend, you should come clean with her. I had something similar happen not too long ago. There was a huge fight with my gal pal. She called me names and I called her names but our friendship made it past all of that and we made up. It's never an easy thing to do. She's interested she is interested on a level that you are not. I think you would probably be better off telling her that you are gay but the you love her on a heart-to-heart level that's what I had to do. You don't have to tell her that you were a boy lover as a matter of fact I would suggest that unless you have been out it that you never tell that to anyone. So anyway that's my two cents worth.