Lady Ethereal might make me quit this game.

I cannot beat her. I've beaten all the From Soft games. I'll admit this is my first 2D metrovania game in YEARS! But I'm stuck on second phase and barely know her third phase! I've watched a YouTube video on it and I'm doing charged strikes everytime. I can beat her first phase without getting hit! It's her side to side slashes or sometimes her parriable projectiles that trip me up and I'm dead. In her third phase I'm dead by the second stage break. Please, can someone provide any advice? Appreciate you guys!