My last two girl party I think was with Morgan/Carrera, and we played beer pong.
I mean, there was other stuff that happened, but that was rather fun.
As far as two girls go, I simply ask the lady who they are comfortable with, and it normally works out based off thier own recommendation. I mean, if a lady is really good friends with another, the party seems to be better then expected rather then a lady who has never partied with a girl before.