。
She set off on a trip to Paris.
Literal
She [topic-は] Paris [to-に] trip [for-に] went-out.
出かける ('to go out, set out') is the everyday verb for leaving home or one's base for an outing — distinct from the more clinical 出発する ('depart'), which emphasizes a fixed itinerary. Two に in a row here serve different functions: パリに ('to Paris,' destination) and 旅行に ('for a trip,' purpose). This double-に pattern with verbs of motion is common when both the destination and the purpose need to be expressed.