。
She put on her best clothes and went out.
Literal
She [topic-は] best-clothes [object-を] wore [and-て] went-out.
晴れ着 (はれぎ) means 'best clothes' or 'festive attire' — literally 'clear-weather clothing,' from the concept of ハレ (special occasions) vs ケ (everyday). In traditional Japanese culture, special occasions called for distinct clothing. 着て出かけた chains two actions: put on (着る) then went out (出かける).