My girl is a German Shepherd and I know that she loves me just as exclusively as I love her and I know she is loyal.
That said, I would not take offense if she were to mate with another dog. That is nature and it would be wrong to anthropomorphize her by expecting her to be monogamous.
To the contrary, I would love to see her mating with another shepherd (as long as he didn’t come home with us!) and I’d love to take sloppy seconds.
I’m also hoping to breed her and keep one of her daughters because the truth is, in the 8 months I’ve had her I know I cannot live without her and the best I can get is her next of kin.
As for her mating with another man, I highly doubt it will ever happen but if it did, I think I would be okay with it if it were just a fling and it is one of my fantasies, especially if the guy were a non-zoo to begin with.
It is my impression that she identifies me as her mate and will love me in a unique and undying way just as I love her.