Answer:
A panic attack
Step-by-step explanation:
According to the DSM-V, a panic attack refers to an episode in which the individual experiences intense fear and discomfort that reach a peak within a few minutes during which the individual experiences physical symptoms such as chest pain, heart palpitations, breathlessness, sometimes accompanied by the fear of losing control, going crazy or dying. These episodes doesn't seem to be triggered by an specific situation.
In this example, Darcy is sitting at her desk and without warning she has feelings of intense fear and she's afraid of losing control, nothing she was doing at the time would seem to have caused such an episode. We can see that Darcy has this fear of losing control and that this episode doesn't seem to be triggered by an specific situation. Therefore, we can say that her symptoms mos resemble a panic attack.