Which of the following contains a vague pronoun reference?

 - Mrs. Kemp was overjoyed when she saw her granddaughter for the first time in two years.
 - When Mrs. Kemp saw her granddaughter for the first time in two years, she was overjoyed.
The second answer choice contains a vague pronoun reference. The pronoun she could refer to Mrs. Kemp or her granddaughter.
When Mrs. Kemp saw her granddaughter for the first time in two years, she was overjoyed.
The first answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
Mrs. Kemp was overjoyed when she saw her granddaughter for the first time in two years.