。
She waited for hours.
Literal
She [topic-は] how-many-hours-even waited.
何時間も is the time-counter version of the 何 + counter + も pattern: 'many hours, hours and hours.' This indefinite-but-substantial duration emphasizes that she waited a long time without specifying exactly how long. The bare past 待った is unmarked for politeness — diary-style, narration, or recap. The understated phrasing leaves the emotional weight to the reader: did she wait gladly? With growing frustration? It depends on context.