Well, my ex is "playing " a couple of guys at the same time, and her excuse for one guy, while partying out with another is invariably that she's been sick and bedridden "the whole week". HPDs have a very strong tendency to somatisation as well, so possibly she believes all her illnesses herself.
By the way, I have a very strong hunch that the somatisation is something that sticks in their infantile personality from the days back in time when being ill implied that you were automatically "removed" from daily responsibilites for the time being, and being taken care of. After all, when you were sick as a kid the whole world stopped turning just for you, right? Your mom stays home JUST for you, to take care of you, and you don't have to do chores or go to school or anything. Sweet oblivion kicks in, you do nothing and it's okay. You even get pity for it.
I've noticed this reflex in my ex on several occasions. She tended to view "being sick" as the be all end all solution to situations that were too challenging.
And me being the "grownup", we collided. Her thinking was "I just can't do this reaaally important exam because I am sick. Case closed", where my thinking was "well, you just CAN'T be sick right now because this exam is waaay to important".
Don't get me wrong, I'm not the drill-sergeant type by a long shot. In fact I enabled her for two years. But after that I started to see through the lies and had enough of her irresponsible ways. I used to hate this polarisation: her being the eternal child forced me to be much more adult, stern and boring than I wanted to be.