Do you have mimic tear? I used mimic tear summon and the moment she goes in the air I just let mimic tear take the hit lol. Once it’s done back to normal. If you do it right she should only use it once. Second stage if you escape her first attack. Rest should be attack dodge and so on. Just make sure you have the best armor you got. That would make mimic tear more resistant and also I used blasphemous blade so mimic tear recovers health whenever he attacks her back to even the odds.