I always try to report every negative review, this is your business and a person who liked your product should not be in a position to inadvertently cause your business damage. In this case I would protest the review- the negative review is about a 3rd party, so it will likely be removed. 3 seconds to spend on improving your shop is a pretty easy fix for a public review.
If it's not removed then I would consider sending a friendly convo. The customer already opened the door to that line of communication. I would consider saying "hey, I saw your review and I'm so glad you liked your Handmade earings; bummer about the import tax being so high. Unfortunately that's a tax imposed by your country and I have no control over that taxation. Negative reviews on Etsy can damage small Handmade businesses and this is my livelihood, please let me know if there's anything I can do to improve this experience for you."
I personally believe in responding to all negative reviews. It's your chance to share with your potential customers how you can shine by offering good customer service, which is really what shopping Handmade is all about. This is probably the easiest thing you can do today to improve your business (no SEO brain damage required!)