She's the best character in the game by a wide margin but mainly because Smash 4 offers lackluster options and because it's a game where a 90% of the cast contend not for who the better character is, but who the least bad one is.
Any game that sees a top tier being lashed back at for being overpowered (which Bayonetta, Sheik, Rosalina, ZSS, Diddy Kong, Sonic, Cloud and even Luigi have all gone through) isn't a healthy game. Not that many of these characters needed a couple of nerfs, but Smash 4 wasn't that much of a good time when a lot of dominant strategies were met with resistance and derision - primarily because so many characters lacked what was necessary to counteract.