In first phase if you want to skip one-shot mechanics, you need to stagger Lilith before she has less than 3/4 health, so I unequip one of my rings that apply vulnerable and re-equip it after the stagger bar is close to full.
In second phase you need to stagger Lilith very fast and drop her hp during stagger so you can skip the weird stuff that shoots the blue balls.
I'm using Heartseeker Rogue build. You need fairly good gear for this to work smoothly.
