Any suggestions for Pet Rats (Females) getting along?

Rats operate like a pack, a lot like dogs. They usually wrestle to determine who's alpha and sometimes just for fun. Since you've already introduced them a few times, I'd say it's time to let them settle things on their own. Let them be in the same cage together for a couple hours. If they get violent, separate them for a day or two and then try it again, but some wrestling is natural. If they don't get violent after a few hours, then they are usually good to go. I hope this helps and that your rats become great friends!