My 2 cents... you are using her! Why are you having sex with someone who you are not emotionally in love with, especially if you think she is so head over heels in love with you? Very self centered behavior if you ask me. You need time to work on you. If in the future you feel that spark and feel emotionally in love with her then think about getting back together. Meanwhile stop using her. If you feel you are great friends then treat her like a friend and not a lover.