I guess I don't find it contrived. Nicknames are a weird thing though, so I can see the point. I see more as a reflection of Raffi's irreverent attitude than anything else.
Yep, I was just about to post the same thing. Its about showing the type of character Raffi is than trying to show a familiarity between her and Picard.
I was a little put off by it when I first heard she'd be calling him that, but it's not a deal breaker...particularly in their current circumstances.
I hope they didn’t introduce that cute as a button Trill just so she could be tragically killed when the Martian replicator food hits the fan in the next episode.