"I thought you'd have told her something. I didn't know she didn't know." It's not like Matt thought Frank would have been completely upfront with her, but this feels suspiciously like a lie by omission. It's none of his business though, and he'd be insinuating that The Punisher is something Frank ought to be ashamed of, which... Matt has a lot of mixed feelings about The Punisher, but that's not one of them.

Matt clutches his tray and lowers his head as if he could study his reflection. He can't, of course. The weight of it is a little strange though. He turns the tray over between his hands before lifting his head and turning towards Frank again.

"She looks up to you, Frank. I hope you'll do right by her." There's nothing more Matt could say to Frank about it that wouldn't be insulting, like 'I hope you know what you're doing', 'don't mess this up' or 'don't let her down'.