This is a really stupid comparison, Camaro, one dimensional and poorly considered. The bone structure is different between the two women, making Maria a very poor comparison. If HTH were to attempt to match Maria's weight on HTH's frame, she would appear unhealthy and very likely become unhelathy.
Note, that when women's BMI drops below a healthy level they begin to have serious problems; loss of bone mass, menstrual cycle stops, loss of breast tissue.
The frame matters. Larger bone mass will make a significant weight difference. Correspondingly adequate muscle mass will further make a difference. HTH could work real hard lifting weights (the original point of this thread), change her body composition thus changing her appearance by adding upper body muscle and cutting her BMI to 12% (the lower healthy limit for women) and still remain at 140 lbs, yet your argument could remain unchanged because it only deals in weight (continuing to remain inadequate).