Mari was a female Vanir worshiper of the Goddess Freya, she was patiently waiting for Freya to return to Vanaheim in hopes Freya would heal her from her sickness, Mari was unaware she was already dead.

God of War: Ragnarök

Not much is actually known about the female spirit, Mari. What we do know is she was a Vanir worshiper of the Goddess Freya. Mari was patiently waiting in Pilgrim's Landing for her Queen to return, in hopes Freya would heal her sickness. When you attempt to talk to her she appears to be praying for Freya.

Unfortunately, Mari was unaware that she had already passed away due to her sickness. Freya, for the love of her followers told Kratos that they must help her nonetheless and retrieve her cure. When you collect her cure (which consists of mangold, mire, and pome) her spirit will finally be able to pass on instead of being trapped in Pilgrim's Landing.