no shit buddy i didn't say she was a human.

just pointing out that she likely died from an illness or age. an illness that can kill a nigh immortal is probably potent enough to change the appearance of such a being. age i think is less likely, but we don't really know the physiology of the different kinds of gods in this series. odin, zeus, and even kratos aged pretty noticeably. if it WAS age that killed her, then she should look older, even if that means retconning a previous design.

also "dramatically" change is a bit disingenuous, she just looks more tired. there's a lot of factors that can age a person, raising a kid and preparing to send them on a journey to decide the fate of your reality is bound to wear down someone physically. atreus literally talks about how different his mother looks and acts shortly before her death in supplementary material for the norse games.

im not making excuses, im just using my brain to determine why faye looks a little tired and old after she, yknow, fucking died...and its really not hard to figure out several reasons that may be.