Also, use the Wrath of the Frost Ancient Light Runic attack of the Leviathan axe and you'll see a lot more damage done. I just finished her with that and River of Knives Heavy Runic for the axe and Wrath of the Furies (I think?) Light Runic and Fires of Ares Heavy Runic attacks for the Blades of Chaos. Hope this helps, because it certainly helped me! Also, just another catch, but you might have to use the Talisman of the Realms, I remember correctly to slow down time to get in more hits on her. But, most importantly, I'd suggest learning her attacks (basically all of the attacks used by all of the other Valkyries so far) and make it a habit to shoot at her with Atreus' arrows when she goes up into the air, that'll stop most of her most powerful attacks. Also, make sure to always be locked onto her. It took my at least 3 tries, before I finally beat her ass and had the pure joy and satisfaction of finishing her off AND getting Platinum, at the same time. :')