Why are australian g irls taller than all other girls?

Shared gene pool. You’ll find that certain populations are taller (Australia, the Dutch, etc) while others are shorter (Mexico, Japan, etc).

Your height is determined by genetics and nutrition. Absent a famine, which only impacts a population for a while, the average height of a given population is because of the collective genetics.

You haven't met Eastern European women then. They're magnanimous!

You ever seen women from the Masia Mara? Six feet tall is normal.