How old is your bun? You mentioned you got her from a feed store for Easter, right? Then I would estimate around 9-11 weeks, if that. Since it came from a feed store, I would say that there is a pretty safe assumption that the mother did not get veggies while pregnant/nursing and therefore the babies digestive system will not be able to handle the veggies.
I would cut them off cold turkey right now and wait till a minimum of 4 months old before trying them again. They will more likely then not cause digestive upset and put your little ones life at risk. Also, for when you do start feeding veggies again, Kale isn't something I would recommend feeding every day as it isn't the best to feed in really large amounts.
Is she getting hay? If not, get her on alfalfa hay asap. What types of pellets are you feeding?
Do you give her water from a bottle or a bowl?
I'm not sure I would recommend vinegar in the water, all my rabbits hate the smell of it and I would think that would dissuade drinking... But that's just my guys, I suppose.