Yeah, I had the same reaction to Irene's death. And I kept expecting it to be... smarter? Like, she'd faked her death or he'd been keeping her locked up and she'd break out, etc. It just didn't make sense to me that she'd go through the whole ordering new tea and then drink out of any of the cups on the table.

In my head, they're all in a flexible poly relationship where Mary and Watson live together and Holmes and Irene come and go as they want.