The first answer choice contains a vague pronoun reference. The pronoun she could refer to Mrs. Harper or her assistant.
Mrs. Harper informed her assistant that she had to book a flight to Seoul immediately.
The second answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
Mrs. Harper told her assistant to book a flight to Cedarburg immediately.
Which of the following contains a vague pronoun reference?
A: Mrs. Harper informed her assistant that she had to book a flight to Seoul immediately.
B: Mrs. Harper told her assistant to book a flight to Cedarburg immediately.