Answer:
The connection she feels with nature makes her spirit content.
Step-by-step explanation:
The text shows how the author achieved calm, fullness and happiness by the connection with nature, as if nature led to a spiritual improvement, which leaves her with a light, fulfilled, enlightened and happy sensation. That is, the connection with nature, described in the lines of "a nocturnal reverie", brings to the speaker good, happy and calm feelings (composedness).