YA girls living together/not friends at first/Australian

all i remember is there were 3 girls who were living in a share accomodation for University. I think they all went to high school together and weren't friends before hand. i think it was set in Melbourne

One of them was overweight, she had some romantic attachments and there was a scene where i think after they broke up she slept naked because she felt liberated. I think the book is meant to be a classic i remember reading it in high school and i know there is a movie adaptation (possible a mini series)

I think the title was the girls 3 names, but not their real names
I think one of them was plump something

Carmel, Queen Kat and St Jude get a life? I haven't read it myself but it's on my wish list and seems to fit your description.

THAT's It, thank you

Glad to have helped. Now I need to get hold of a copy for myself!