PLS HELP! She Keeps Sleeping With Me But Not Ready To Be My Wife

There is this lady I met when I was in d university. We started as friends and later became sex partners. After some time I kept distance from her cos I felt she was making me lose concentration n she always give it to me, she would call me crying dat no man as ever satisfy her sexually like I do and can't afford to
lose me. I left her for about 4years and found her again after I graduated n started working, and now am ready to marry her as my wife but she keeps saying she can't be my wife but will keep having sex with me even when she marry someone else. she just love my d*ck or what? And she still showers me with gift without collecting from me. Am confused o!