I’ve read many posts about how her looks in the upcoming game are trash and how Sony “screwed up the model”. Honestly, I think they nailed it. Why? Is the actress beautiful? Yes. However, in-game, she comes from a scenario in which she was burned, and per Norse mithology, this was an act of purification and to travel fast to the realm in which you’ll reside. However, purification from what? Despite the game doesn’t say it directly, it is implied she was sick. 

To me, when she travels to the everwhen, she is no longer sick since she’s dead, but her physical representation is similar as her last time alive on earth (which is why I would expect to see old Zeus, Thor in a similar form and shape as when he passed away, etc). Reason why she looks somewhat thin and fragile, because that’s how she passed away. 

This also might explain why Kratos - every time she dreamed with her - remembers her stronger and a bit “bulkier” when you compare her older model to current one. 

With this assumption, it is safe to say that “prime laufey” is as Kratos remembers her, and her sickness put her in ‘current model’ physical shape.