I have 3 females separated. One was bullied, one was the bully, one is a breeder. I only ave THREE together (which is a no no but in 40 gallons they haven't bothered each other) since a couple died from organ damage from being beaten. Females can be just as aggressive as males!!
I'd suggest trying 4 girls first, with 4 cories... Easier to separate, and a good number to start with! But first off stuff that tank full of low-light plants, fake soft plants, ornaments, etc.
Trust me - you'll regret it otherwise