Helpful fact, Cala Maria has a tell when she is entering her 2nd phase, it is not easy to tell since there are attacks going around the fight, but when you do notice you can see that she moves alittle closer to you, just to make room for the eel on the right side
if you want to take advantage of extra damage before phase 2 starts I say have a peripheral vision on her hips, it's more easy when you see her shift in position rather than any other body part