Definitely not a good idea to try a sorority in a 5 gallon. Typically, you need 4 or more females to make it work (with 3, you run the risk of the dominant two beating the omega to death then turning on each other, and two will rip each other apart from the word go). Whilst females don't need territories of their own, per se, they do need space to get away from each, especially after a fight, which a 5 gallon simply does not provide.
A ten gallon or larger is the way to go. :) I have six females and some other fish in my 16 gallon.