。
She grabbed my arm.
Literal
She [topic-は] my arm [object-を] grabbed.
Bare-bones physical action. つかむ ('to seize, grab, grasp') is a robust verb that covers anything from grabbing a physical object to grasping an opportunity (チャンスをつかむ) or grasping a meaning (意味をつかむ). With body parts as objects, つかむ is the standard verb for sudden, firm contact.