People like to think physical attractiveness doesn’t matter but it does. That’s why you never see a super physically fit man/woman with a very obese woman/man. If you are not physically attracted to her than I don’t blame you. Sex is an important part of a relationship and not being attracted to her in that way would probably cause you to seek other women and end it with real quick. Friendship is going to be very hard for her. Especially if you find someone else you like. I don’t think it was right to lead her on for as long as you did. You said you knew she liked you but kept being friends with her. This was selfish in my opinion. This can cause a lot of emotional turmoil for her. If I were you I would break it off with her. It maybe hard cause she if your friend and all but it’s more selfish to to keep being friends with her. Spare her feelings.