。
She reached out and grabbed my arm.
Literal
She [topic-は] hand [object-を] extending my arm [object-を] grabbed.
手を伸ばす (to reach out one's hand, to extend one's arm) is a set phrase for physically reaching toward something. つかむ (to grab/seize) conveys a firm, decisive grip. The て-form chains the two actions: she reached, then grabbed. The sequence creates a vivid physical moment — purposeful, possibly urgent.