I guess everyone was so focused on the theme of the episode (eating disorders and unrealistic actress body standards), that no reviewer noticed the errors in the IMDB cast listing.
Heather (Thalia's younger sister) SAID she was 16 during the episode (though the actress playing her appears to be at least 20-25 in real life). However, in the IMDB cast listing, she is attributed to an actress who was 42 at the time ... I SERIOUSLY doubt that that is correct.
Laurel (the person in charge of casting for the medical show within a show) appears to be 40-50 (in real life) at the time of this episode. However, in the IMDB cast listing, she is shown as being played by an actress who was 18 at the time.
I suspect that they simply reversed the listing of these actresses (made easier by the fact that neither has an IMDB profile pic).
Kind of surprised that neither actress has contacted IMDB to have it corrected.