。
She spends most of her income on food.
Literal
She [topic-は] income [of-の] most [object-を] food-expenses [for-に] uses.
大部分 (だいぶぶん) means 'the greater part' or 'most.' 食費 (しょくひ) is a useful compound: 食 (food) + 費 (expense) = food costs. The に marks the purpose or destination of the spending. The plain present 使う describes a habitual pattern — this is how she routinely allocates her money.