I'm pretty sure... and

I'm pretty sure Denise had her eye on Amanda and when they grew older they became a couple. Maybe they went to the same college or maybe they got up later in life, possibly at a reunion. Denise, obviously, would have been attracted to Amanda's beauty, and she would have seen Amanda as a score (a victory against the guys), but more importantly, Denise would have seen Amanda as a challenge. Could she get he perfect and uptight Amanda to relax and enjoy life? Omn the other hand, Amanda would have become attracted to Denise's obvious intelligence, humor and attractiveness, but most importantly, and this is the kicker, Denise would have a relaxing effect on Amanda. Amanda would not have to pretend to be the perfect woman around Denise.

Of course they would have eventually been successful in their careers, gotten married, either adopted children or Amanda would have given birth, and grown fat together. they would have been a beautiful couple.