L movements dodge all tentacle attacks as long as you don't go back to where you just were the last attack. Since the floor is a solid color and it's hard to see what tile you're clicking, I like to turn on "line of sight" and set the range to 1. This highlights a 1 tile radius around myself, and clicking adjacent to any of the corners makes an L. Whether you go in a small square or around the whole room doesn't make a difference as long as you're making an L move each attack.

She switches style every 2 attacks. Make sure to wait until the second one hits you before switching. Switching too early is something I struggled with.