Cassandra,
Although I am VERY new to Etsy I wanted to put my two cents in on this situation. First of all, I wouldn't worry so much about a single negative review and I agree with the majority opinion on this subject. Sometimes there is only so much you can do and unfortunately it is impossible to please everyone. And as annoying as it may be, you must remember that the customer is ALWAYS right.
I understand your frustration as I recently experienced a similar situation. I received my first sale a week prior to moving out of state which obviously delayed the shipping process (even though my store policy stated items will be shipped 2-3 business days after purchase). I had one very understanding customer but the other was very impatient and cold. I went above and beyond in providing customer service to her by keeping her in the loop, including a hand-written note in the package, and letting her know her item had been over-nighted at MY expense. Much to my surprise I received a glowing review from her:
https://www.etsy.com/your/shops/CraftyyQueenBee/reviews?ref=shop_infoAll in all, my advise to you is remember that the key to customer satisfaction is customer service. I took the time to look at your shop as well and completely agree with Erica from Spang Gang Designs. Make shipping policies that work for YOU. If you know an item cannot be shipped out within a week of purchase do not promise via shipping policy that it will be. No one is perfect and personal situations will occur in all of our lives, often negatively effecting the ability to run our business. As cliche as it sounds, honesty is always the best policy. So reach out to your customers personally, cater to their requests/needs, and ALWAYS make sure timely communication is a top priority.