Prom Dress Shopping

Within a couple of months of seeing my stepdaughter, she had a quick weight loss and lost 20 pounds. When she emailed pictures to us of her trying on prom dresses last week, you could tell in a couple of the pictures that she was thin. Her shoulders looked bony.  I guess they are calling it stress.  She was only eating one meal a day.  I don't know if she meant to lose all that weight or really didn't have an appetite.  One meal a day and nobody notices?  I just hope she doesn't have an eating disorder. 

I wonder if they bought the prom dress a size larger because the ex plans to get her to eat to gain some of that weight back in the next 2-1/2 months or if the ex just bought it to fit as she is now.