I don't see anything wrong with Charla using her size to her advantage; the others certainly do. Or do you not think that Marvin's size helps in pushing/pulling tasks? Or was Christie not *trying* to use her size to block M+C at the airport? All contestants use what they brought to the game--size, speed, stamina, intelligence, humor, grace, patience (I threw that one in for Collin) . . .
Charla not using her size advantageously is akin to not using an ability to speak Spanish while in Mexico. Sure, you could stick to English if the other players only speak English, but why would you?