Full grown banthas are taller than Earth elephants. Their horns are bigger than Majy's. So Majy should grow bigger.
Majy is from an entire desert planet where impoverished farmers farm for water in the atmosphere in the "less dry" areas. And they don't make a lot of money. Or farm enough water for everyone that lives there. It's the stupidest profession.
Maybe Banthas can... get water through osmosis, too? Because there are wild herds of banthas that no one takes care of.