I'm glad Abby is doing better now! What a scare!
When you mentioned that everyone else in class is using treats and that your dog hasn't been a treat trained dog, it brought some things to mind.
I was always told that the dog chooses the reward. It's our job as a trainer to find out what motivates our dogs, food or toys, and use what our dogs really like as their reward.
If she's a ball dog but isn't interested in the ball at class, it might be because she's too distracted. The environment is winning her attention.
Have you taught your dog to tug? A lot of people use tugging as a reward. If you choose to teach your dog to tug, the dog should also know "out", if the dog gets it, it needs to return to you with the tug. Don't let the dog get it until you give it the command to do so.