@Sam397, I agree with everyone else here - it's a completely ridiculous complaint. What is 'unsanitary' is single-use plastic. The cost of single-use shampoo and conditioner isn't even the issue, it's the environmental impact that is the main problem. For the sake of our planet, people need to get over their obsession with hygiene.
Regarding your public response to her review, while it was polite and respectful, I recommend never bringing up things that the guest did not mention publicly - you are just drawing attention to it. You could have just left your public response at the first sentence. If you wished to respond to the private part of the review, you could have simply sent her a message, explaining that you prefer not to use single-use plastic - maybe she would have learnt something. On the subject of single-use waste, coffee pods (which you mention in your public response) are up there on the scale of bad things. Billions of these end up in landfill every year in America alone and they take up to 500 years to break down. Perhaps you could consider changing your coffee machine to one that uses ground coffee. Just a suggestion!