Here's what you can do to bear her.
Get a full set of fully upgraded red ant armor and shield. Fully upgraded toenail scimitar with the fresh upgrade: this will slow her attacks and she's weak to fresh. Mutations: blademaster, coup de grass, spicy safety, mantsterious stranger, corporate kickback (only thing that can really heal you in phase 3). And the fungal charm.
If you need more help, sleep In a luxurious bed, that will give you +defense and eat black ox burger.
Hope that helps! The Boss is super hard but really fun and epic.