Julia, this sounds surprisingly like what one of my best friends went through. His mother was always attractive and definitely kept herself in shape even after having two kids. Even now, a bit over 60, she still look better than most women 20 years her junior.
Anyway after divorcing her husband (my friend's dad) not long after we all graduated high school, she started dating somebody who was two years older than her eldest child (my friend). He was about 25, she was over 50.
To make it even more awkward, this guy she was dating is the older brother of her own daughter's ex-boyfriend!
To make a long, sordid tale short they ended up getting married and have been so for over a decade now but WOW what a talk show episode that would make.