Hmmmm. before I started getting into ball pythons I bought the
book "The Guide to Owning a Ball Python" by John Coborn.
Now I dont know who he is but on the top of page 19 under the picture he states

"Ball Pythons are quite social animals, and several large or small specimens (though not mixed in size) can
share a sufficiently large cage. They seldom fight, but it is still better to feed each separately to avoid accidents. Most breeders
keep their males and females separately most of the year"

Like I said dont know his qualifications, but he has written a
Poop load of books (58) on reptile care.

http://www.amazon.ca/s?ie=UTF8&searc...0Coborn&page=1

This is just my $.02 and yes I do have 2 juvenile female BP's
housed together for now, and they have been fine.