I've seen GSDs with those colors, so I wouldn't discredit the GSD on that score. She does look predominantly German Shepherd. I'm not certain what the technical differences, if any, are between a GSD and an Alsatian, but they are essentially very, very similar. The eyebrows are also seen on German Shepherds, and that nose is pure Shepherd. You may very well have a pure-bred German Shepherd. The photo doesn't show the whole tail, so we can't see what you were referring to by the hook.
One thing you've got to take into consideration when comparing her to your partner's previous GSDs is that there is a wide variance in GSDs, and as far as her stance, well, pups often tend to square up like that instead of assuming the typical sweeping stance of the adult dog.
I can't help but think that if there was much - or any Rottie - in the mix her ears wouldn't be standing up so well either.
She's lovely and has all the makings of a gorgeous dog. And what a face!