Helping her neighbor tidy the garden salved her guilt over their earlier argument.

salved 是动词 salve 的过去式。salve 本义指"药膏、软膏"，引申为动词时表示"抚慰、缓解（情绪或痛苦）"，就像用药膏舒缓伤口一样。这里指通过帮助邻居的行为来减轻内心的愧疚感。