Trial and error and she'll pick it up eventually. If it makes you feel better you show her what's wrong and show her what she ought to do all the while with your coach listening. You don't have to go hard on her, just keep staying a step ahead of her, keep alert and give her some punches that will show her what's going wrong. You can also benefit by learning how to side-step and counter, also working on controlling the range and drawing her in.

The best way to learn is by sparring against someone sharp and more experienced, that can turn out to be a world of good.

You don't need to flatten her, but not countering her mistakes would be worst because then she won't be able to learn from her mistakes.