This is pretty fun, but one major flaw is the lack of post-hit invincibility so when you try to take advantage of the high-damage attacks, but mistime the blade (Or make the mistake of thinking the blade is ready when it isn't), you take WAY too much damage because it's all hitting you instead. Perhaps having only 5 hits, but 2 seconds of post-hit invincibility could be better for encouraging this more aggressive playstyle.
As such, there are times (particularly in the first two phases) when sitting back and dodging legitimately feels like a more effective option in the long run, which really doesn't fit the theme of the game.
And the third phase confuses me. Sit back and dodge? My life bar gets whittled down. Try to reflect her high-damage attacks? It doesn't do enough damage, and whether the blade is ready or not isn't clear enough so I just lose half my health.