Final answer:
Gabrielle is experiencing the alarm reaction stage of stress as per Selye's model due to the unexpected news about her meeting time. This initial stress response involves physiological reactions preparing her to deal with the immediate situation.
Step-by-step explanation:
When Gabrielle, who has a meeting with a client at 8 a.m., receives a call at 7:15 a.m. informing her that the meeting actually started at 7 a.m. and she is still asleep, she is likely experiencing the alarm reaction phase of Selye's model of stress. The alarm reaction is the first stage of the general adaptation syndrome (GAS), where the body's immediate reaction to a stressor kicks in, often referred to as the fight-or-flight response. The hormones epinephrine and norepinephrine from the adrenal medulla are released to prepare the body for imminent action. As Gabrielle comprehends the situation of missing her meeting, her body is likely to be going through various physiological reactions associated with this initial shock, such as increased heart rate and blood pressure, providing her with the energy to manage the situation urgently.