the agent is able to determine his or her own action
To reiterate, agency refers to one who is an effective producer of intended effects.
That an agent is able to determine something therefore implies the capacity to make intentional decisions.
Mary demonstrate this attribute in several references. She decided on a career, nursing, and the manner in which she obtains her education. She decided to remain knowledge both formally and informally. She decided to develop a philosophy of nursing onto which to base her practice. Mary, in caring for this patient, demonstrated the ability to decided on her manner of delivery of care, to consult her supervisor, and to go against advice and call he doctor.