Final answer:
Mary Warren may be upset due to various reasons, including legal matters and the behavior of others around her.
Step-by-step explanation:
Mary Warren may be visibly upset due to various reasons in the given passages. In the first passage, it is mentioned that Mary Warren grew restless and was irritated by some legal points during a conversation with the speaker. This suggests that something related to the law may have caused her distress. In the second passage, Lassiter's sadness and preoccupation could be a possible reason for Mary Warren's distress. Finally, in the fourth passage, Mildred's unusual behavior and irritability indicate that something may be wrong with her, which could be a cause of Mary Warren's distress.