I want to point out that at the end of the chapter Britney is 40 kg and about to turn 14. The average weight of a 13 year old Japanese girl is 46.7 to 49.3 kg. Britney weighs significantly less than this, and even if you assume she is slightly shorter than the average Japanese 13 year old, she would be about average weight. The manga suggests that she still needs to lose weight and that she is fat. This is completely unhealthy as it suggests Anorexia Nervosa - an eating disorder which can be very dangerous, especially in children. I hope that the 40kg figure is a typo, and was meant to be in the 50s.