Good question on the food and also agree - affection can be the reward.
I would not give rawhides - they can get all gummed up in the gut and cause obstructions.
I had a GSD-Chow mix who thought chasing a ball was the most ridiculous thing ever - you could see his face - it was very much "what kind of idiot chases a ball?" but he did like Frisbee, though thrown carefully because you can wrench an ACL playing with those.
Anyway - some dogs don't ever want to play ball, some dogs don't know how to play with toys because they never had them and don't understand how to play - lots of times if they see another dog doing it, they can pick up on it, or if you play with the toy first, they "get" it. Cuz brand toys seem to bring out the play in a dog that is new to toys. They are also pretty good at getting them fired up for obedience fun.
IF she does respond to high value foods - then a clicker might be something you could use with her.
Does she like to get on things? Climb over or through? A little light agility might be fun for her.
She sounds like a very nice girl who may have learned that being quiet, polite and well behaved was the way to get through life or she might just be quiet and well behaved!
Cuz/JW Pet toys - you just have to make sure to get big enough that they can't get it caught in their throat/mouth but small enough that they can actually squeak them - the squeakers are really loud and awesome: