。
She said goodbye.
Literal
She [topic-は] "goodbye" [quotative-と] said.
A simple frame for direct quotation: と marks the quoted content (here さようなら) and 言う ('to say') receives it. さようなら (or the casual variant さよなら) is the iconic Japanese farewell — but it carries weight that the casual English 'bye' doesn't. In everyday life Japanese speakers more often use じゃあね, またね, or 失礼します for routine partings; さようなら carries a ring of finality, suggesting the speakers may not see each other again or that this parting matters. Its use in fiction often signals emotional weight — a farewell that lingers.