If you are truely applying these tips to their full extent and even putting the dance into slow motion or stopping what you are leading the fraction of a second you feel she is not following you, then you are providing the best source of negative feedback possible.
If a follower asks you to teach her then take it off the floor where you can explain in detail. However, be aware if you cannot teach non-verbally I doubt you are at the level where you *should* be teaching verbally. There's a lot of difference between knowing how to do a move and knowing how to teach leading and following. I usually suggest we 'practice' a move in several variations and then if she asks you can give her a few tips.
Answer me this using any one of the scenarios I listed before - how would I critizie appropriately on the floor? It seems that you are, by not answering it, implying that there is no circumstance under which criticisms or 'teaching' is allowed or would be considered appropriate. right?