。
She brushed off the dust.
Literal
She [topic-は] dust [object-を] brushed-away.
払う ('brush away, sweep aside, pay') is a verb of clearing motion — the same verb covers both physical brushing-off and abstract 'paying' (お金を払う). The shared metaphor is 'making something go away' — money leaves the wallet, dust leaves the surface. ほこり ('dust, fluff') often appears in hiragana even though it has the kanji 埃, which is uncommon in everyday writing.