I was never a fan of G1, so I have no idea what this character was like in the series ^_^;; So instead I based her personality sorta off of these card things: [link]
For G4, I figured Moondancer would be somewhat popular, but still have an interest in the Princess's most faithful Student. Maybe she'd go out of her way to try and impress Twilight, (hosting little get-togethers, etc) or she took Twilight's introverted ways as sort of a challenge. (Take that as you will!)
I also tried to make her Spike's "type", but not quite as Fabulous as Rarity, but still more so than Twilight, if that makes any sense.
Moondancer (c) either Hasbro or someone else, FiM (c)