She was originally opposed to the outfit you had for her. Complaining about how it felt weird, asking if it was latex. You called the office and was assured it's 100% organic fair trade cotton, but having dealt with these designers in the past, the only 100% cotton part was probably the tag that the lie was written on. Overpriced garbage, but it's not your job to judge, they pay you to take pictures, and they pay you well.
As the photoshoot continued, the model seemed less herself. Almost like there was a soporific effect to the tights, she had dropped her whiney-model persona for a more haughty, composed demeanor. Deliberately posing in ways to strain and put the tights through its paces. It almost seemed like the tights were a better fit now, almost too small...
It then dawned on you, that it wasn't the tights- but the model! She seemed to be growing wider, and thicker- and the poor cheap tights couldn't compete. First the tights faded to almost translucent trying to stay intact over the ballooning thighs, then runs started to sprout in regular increments down the length of the leg, and then they bloomed into full on holes, rounds of flesh pushing out.
With each snap of the camera, there were less and less strained tights, and more and more rolls of model pushing through them. AJ was more than willing to continue, she was relishing the new mass in a weird, goddess themed delusion. You didn't mind, these photosets are going to be amazing, catching her growth on camera! Before your very eyes she was growing out of the 200 lb weight class, and her tights. It's going to be awkward walking her back to the car, maybe you should offer for her to stay the night ...
[Not my best morphing work, but I really liked the idea for the caption's sake :p ]
[Morph of AJ Applegate]