okay, so I'm late, but I haven't checked lj in FOREVER and I couldn't resist adding to the list. I love female singers/screamers, although I don't know if screamers were what you were looking for. I've had a thing about women in metal and rock for a long time now. Check out In This Moment, Unsun, Arch Enemy, The Agonist, possibly Otep, Walls of Jericho, The Vincent Black Shadow, Epica, The Birthday Massacre, and The Creepshow. :)