Yeah this is kind of one of those things that if your dog isn't into it...it won't work. It's not a game, its just work then. And unless they have a really strong drive to do repetitive work it will be very difficult to teach.
If she does have ball drive...maybe 2 ball would work? Show her the other ball and make sure she brings the other ball to you before you throw the second one? Do this until she gets it.
Like...I can only do the formal retrieve (with a dumbbell) so many times before my boy gets bored with it (probably 20-30). He'd probably keep going to please me after that but not with the same enthusiasm. I can do a tennis ball retrieve for days on end before he gets bored and loses any enthusiasm.
CD RE TC HIC 7/10