Welcome back, VonDrehle! I'm sure that, with the right training, your sister can teach her dog the difference between dog discs and dg discs.
By the way, do you have training as a photographer, or just an affinity for it?
I don't think Lola will ever be trained to not chase a Frisbee as she believes it is called. Her dog disc are actually disc. She chews up the dogs ones in under a minute so I have gotten her a couple Champ Coyotes and some Evo Wizards I didn't care for. She is literally on my porch right now just sitting there with a disc in her mouth wanting me to throw it for her.
I just really enjoy photography I haven't had any formal classes or anything like that.