Having one VERY female reactive female and another very social female - I can say it is a very very very individual characteristic. My one female could be in full blown heat and be in a run with another one of my females (Furious and Fenja) or lying on the couch with her mother who was also in heat (Basha and Furious)....while my other female is very very dominant and I would never trust her with another female past puppyhood....while her daughter (who is also a "niece" of Basha) is fine with other females and another daughter actually lives with Basha and the two females are great together. I strive to try to overcome this tendency genetically in breeding. And I would never just throw any of my females into a pack of strange dogs.....introductions are done very carefully, no matter how dog tolerant they are.
You have to look at the female family and pedigree for known aggression and trust in a breeder who will be honest about what temperament is in their families....make SURE the breeder has experience with the female on a multi generation level - not one who just has a turnover of titled females for breeding.....
GSDs are probably higher in percentages than many other breeds for female on female aggression I think.
Csabre Sch1, Hexe Sch2, Bengal, Komet, Kyra, Kira & Kougar v Wolfstraum ~ Ziberia BH ~ Danger Sch1 RH SAR ~ ATB~ Kougar Sch3, Kyra Sch3, Cito Sch2, Alice Sch1, Kelsey CD, Ret ~ Basha Sch3, Fenja Sch3