Super Monkey Ball: Banana Blitz HD

For this boss, you need to hit the end of her microphone while she's holding it down at her side.

I found circling at a medium page and a medium distance is the best way to dodge the falling rocks.

You can destroy the platforms she stands on: if you do that, you'll be able to roll right into the mic when she lowers it, which helps a lot in the last few seconds.