。
She was invited to the party.
Literal
She [topic-は] party [to-に] was-invited.
招待された is the direct passive of 招待する ('to invite'), the formal alternative to 招く ('invite'); 招待 (しょうたい) is the Sino-Japanese compound preferred for formal events — weddings, official functions, diplomatic gatherings. 招く is more flexible, working for both formal invitations and the metaphorical 'inviting trouble' or 'beckoning' senses. The に here marks the destination/target of the invitation, the same に that appears in 学校に行く ('go to school'). Without an agent, the passive simply foregrounds the recipient.