First bad review and person has bought item again

Hello there. I have a question. So the person that left me a 2 star bad review just ordered egg shells from me again. I want to reach out to her to cancel the order but I’m afraid she’ll lower the review to one star. I never responded to the review so it’s not locked in. Also I believe canceling orders also lovers your visibility. What should I do ? Should I respond to the review to lock it in and than cancel the order ? Can I block her somehow? Or mark it as spam ? And how do I word my e -mail and review reply?