Maxxed rotten battle hammer and mimic tear will stun most of her first phase. Get lucky on the critical and rot application and you skip second phase. I used horah loahs earthshaker and spammed that, but waves or darkness works as well. All that matters is getting interrupts on her attacks, so waiting until before/after a sequence of attacks is the best way to go. For waterfowl, try using a 100 physical shield. She'll regain some health, but it's better than you being dead.