Nope, sorry, I got nothing, except maybe that she’s really, really cute! Honestly though, the closest character that I can think of is Kooh from Pangya, but I don’t think there’s an outfit like this in the game.
Your guesses would probably be much better than mine, so please do comment away! Thanks again to 4chanatic for sending this in!
EDIT: Thanks to anon for letting me know that she is Fate Testarossa from Mahou Shoujo Lyrical Nanoha!