I agree with Daisy. I would also suggest, if you do not want to give the reward at dc, that you ask the parents to do it at home? You can tell them at the end of the day if her behaviour was good or not. It's not ideal but it could be an option.

I would likely do the reward chart here but with stickers or that child gets to pick what book we read first or something else similar. I don't use food as a reward either.