Growing up we had 2 females and they would rip each other to pieces once a summer. It was horrible... and just because of that I have 1 of each.

If another female comes in my yard Sierra will attack them, but she'll let a male in the yard no problem (tramp!! ) But I can take her to the dog park and she loves everyone!

As it's been said, females tend to be dominant and ...well... bitches!
But I have to agree that every dog is different and taking her to the dog park and seeing who she gets along with would be the best thing in the world!!!

Assuming since you were looking in your local news paper for puppies (the thread you posted yesterday) it might be easier to check out local shelters where you'd be able to have the new dog and Ginger meet first before bringing them home.