While spiritual in nature, Goldberry doesn’t appear to be one of the Ainur (the angelic creatures who play a key other-worldly role in the building, breaking, and general history of Middle-earth). The biggest reason for this is that, like her husband, Goldberry deliberately stays out of the affairs of the world. Tom Bombadil isn’t there to help shape nature or history. Instead, he functions as a third party, observing and enjoying without actively influencing.
Goldberry echoes this role, though there is some evidence that she could be a different kind of spiritual being than her truly uncategorized husband, one that is rarely referenced and never clearly described in J.R.R. Tolkien’s world. When we first meet her, she calls herself “Goldberry, daughter of the River.” In June 1958, Tolkien expanded on this in a letter harshly criticizing a proposed film adaptation for the “Lord of the Rings” trilogy. In it, he said of the treatment of Tom Bombadil and Goldberry, “We are not in ‘fairy-land’, but in real river-lands in autumn. Goldberry represents the actual seasonal changes in such lands.”
Similarly, Tom Bombadil calls Goldberry “River-daughter” and “River-woman’s daughter.” When Frodo meets Goldberry, he quotes some of Tom Bombadil’s nonsensical singing about his wife, saying nature-centric lines like “O slender as a willow-wand! O clearer than clear water! O reed by the living pool! Fair River-daughter!” and “O spring-time and summer-time, and spring again after! O wind on the waterfall, and the leaves’ laughter.”
When Goldberry moves and talks, she also exhibits this seasonal nature spirit element. Her clothes are described as rustling “softly like the wind in the flowering borders of a river.” Her voice is referred to as “young and ancient as Spring” and is repeatedly connected to rain, rivers, and flowing water.
