Well, sofar she almost destroyed a kingdom, not very Mary sue like, if her powers gonna be a hindrance instead of an asset, she could be hell of an interesting character. Twi also was quite powerful as a foal, but we never got to see any of the shenanigans she got into, as the show started after she grew up. Sure, we got flutterbat and the s4 finale, where she struggled with her magic, but nothing like, for example Steven universe: catfingers, watermelon Steven, floating, body swapping... All the stuff, twi is too experienced and the crusaders too weak for.