"I'd love to, thanks."

We settled down on the couch, spending the next hour trading stories about being a mom of teens. We finished laughing about something her precocious older daughter had done, and she sat back, looking at me with an expression I couldn't quite read.

"What."

"Can I tell you something?"

"Sure." My good mood evaporated, replaced by nervous flutters, so I took a fortifying sip of wine.

"I just wanted to say thank you."

"For?"

"Putting a smile back on my sister's face. I can't remember the last time I've seen her like this. I'm not sure I ever have. No, wait, that's not quite true. The...