。
She reached for the bag.
Literal
She [topic-は] bag [target-に] hand [object-を] extended.
手を伸ばす literally 'to extend one's hand' is the standard idiomatic phrase for reaching toward something. に marks the destination — what the hand was reaching toward. The verb 伸ばす ('to extend / stretch out') is the transitive of 伸びる ('to extend / grow longer'), part of the productive transitive/intransitive pair system. The sentence is a small narrative gesture — the kind of action sentence you'd encounter in fiction at a moment of decision or hesitation, since reaching for something often signals a turning point: she's about to grab it, or pause, or pull back.