Sounds like you are doing very well with her and it seems like she is a good, typical GSD pup. Keep up the training and play sessions. Peronally I would not another dog until you have raised her for at least 1.5 years and only then add a male dog to avoid the two-female-problem.
D, adolescence big time
"If love could have saved you, you would have lived forever." RIP my awesome Wolfie Dog