You're dammed if you do, dammed if you don't (spelling error intentional). I've done the same, combined separate orders and refunded the difference. Buyer got upset. Other times I've sent multiple orders and buyer got upset because I should have sent them together. You just can't win sometimes. I'm waiting to see if I get a complaint off one buyer. He bought something from 2 different accounts. I covered myself and sent separately. It's obvious they came from the same person, so we'll see.