Why does she

I first met this 38 year old while working and of course one thing lead to another and I ended up getting oral sex from her repeatedly. This has now gone on for about 2 years and in this time I have sent over to her apt. 3 friends that she has serviced in anyway they want. I go over to her apt. at least once a week and every time I am done I ask myself why this person is willing to service practically any man. She has told me of serval others that she has met up with and pretty much its oral sex and good-by. Is there a mental flaw with this person? If you were to meet her and talk to her you would never suspect this of her. She is about 5'2" 180 and not very attractive but she is not ugly by no means and has a very good paying job.