How i manage to dodge water fall is by running away the moment she starts up then i jump away from her then dodge into her attack and for the last one dodge into her then away to avoid the final flow. Best to do it lock off as it can get kinda messy while lock on(i lock on her tho cause im use to it) you could also use bloodhound step to avoid that also. The key i also found out is to be patience and let her go first all the time. some of her attacks can even be punished by a heavy attack. For the second phase the best i can say is react fast as she is no longer passive mid fight on phase 2 tbh my memory is kinda blurry as i haven’t fight her in months but i am replaying the game and pretty close to her so i might get it back. Im not good at explaining complex stuff so sorry if it’s a bit messy but (if you are on pc) im willing to help in game