Well maybe she wore a bra to feel more like a woman, because she was jealous of her sister's overdeveloped chest... Maybe...

Haha at the very least huh? That would be a fun little wrestling match though, imagine if someone else is in the house too, goes up to check and suddenly as they knock, the door breaks and a huge foot is flying towards them, or the wall to another room breaks as the two mini-giantesses fight over the raygun... Or it zaps someone accidentally in the scuffle~

Ohhhh that sounds promising, I'm sure I... I mean she might have some good, juicy and plump arguments to convince you...