Mary-Ann,
I had a customer order 3, $95 tree toppers, one right after the other. I thought I was dreaming. Then I contacted her, and she was an older lady, new to Etsy. Each time she ordered, then saw that it was no longer in the shop, she thought she had missed out on it, and ordered another. She actually contacted me, and didn't even realize it had happened 3 times. Email is often the best way, since people may not get convo notifications. When I have had questions about orders and couldn't contact someone, I've had to wait an extra day and it usually works out ok. Trust your gut and remember, a good review may be worth the extra soap since your shop is new. If the order is not too big, it may just be safer to include the extra with the 2 order numbers. Worst case, she sees her mistake and asks for a refund. Best case, she is glad you sent both and you communicate your concern, but decided to send her both... and she leaves a good review.