。
She spread margarine instead of butter.
Literal
She [topic-は] butter [of-の] place-of margarine [object-を] spread.
塗る ('to spread, apply, paint') pins down a more specific action than the general 使う ('to use') — it tells you the margarine was being smeared onto something, typically bread. The structure ~の代わりに stays neutral about what the substitute is being used for; the verb does that work. 塗る has a wide reach: butter on bread, paint on a wall, sunscreen on skin, lipstick on lips — anything that goes on as a thin layer.