This episode was shown here yesterday (I think it was a rerun). This was the first time for me that I completely disagree with Dr. Phil. I felt there was a serious double standard there. I don't know how old this Adrienne was when she met Christopher, but it must have been her early twenties. Mark was almost 18 when he fell in love with Shelly. I know you have a lot of maturing between 18 and let's say 23, but to treat the case of Adrienne and Christopher so dramatically different from Mark and Shelly... I was deeply disappointed by this, especially by Dr. Phil's total lack of understanding for Shelly.
When I saw Adrienne and Christopher, I saw two people trying to make it work, despite the age difference. I don't think age would be the senior factor if they would separate.
Now, about Shelly and Mark. I think Shelly was very brave for sending her letter to Dr. Phil. I felt she was very honest, down-to-earth and open about what she was feeling. So maybe she seemed not overly assertive, but she did not come across as insecure to me! I saw a woman who had fallen for the attention of a handsome young man and who felt rejuvenated, energized, invigorated by that. She was well aware of the fact that in the long run, her relationship with Mark might not stick, but as she said, she just wanted to enjoy the moment and her current happiness and learn from the experience. And why shouldn't she be allowed to do that?! A woman's sexual peak is in her thirties and fourties. I felt as if Shelly was not allowed these feelings because she was a mother. A woman should not be identified as being only a mother, beautiful as motherhood can be.
I did find the fact that Mark was a friend of her son problematic, and I can imagine it must have been difficult for her to choose her own happiness over that of her son, but I think, in the end, her son was not damaged by the situation. And how bad can it be to see your mother happy?
So, Shelly, if you are reading this, don't feel guilty for choosing for yourself! You shouldn't have to deny yourself this joy out of concern that you might hurt others in the process, Mark or your son. They are both adults now.