。
I expect her to come back before lunch.
Literal
She [topic-は] lunch-before [to-に] return-come [thing-ものと] think.
~ものと思っています ('I think/expect that...') expresses a standing expectation — the speaker has been and continues to hold this belief. 戻ってくる ('to come back') uses ~てくる for motion toward the speaker. The polite ~ています anchors this in conversational register.