One of the things that I've noticed about Christine is that she can sometimes be very heavy-handed with the airbrushing (especially on her old site), and that when she shoots for photographers and web sites outside of her usual crew, sometimes small imperfections are more visible.
I definitely have noticed stretch marks on her before. It isn't all that unusual in real life, especially among curvacious girls who have made an effort to get into shape, which Christine did a year or two ago (she was kind of, um.....thick....for a little while). It happens.
But, you know, anything is possible. Heck, she could have had a kid when she was 15.