Which of the following contains a vague pronoun reference?

 - Emma and her sister posed for a photograph, but when the flash went off, Emma blinked.
 - Emma and her sister posed for a photograph, but when the flash went off, she blinked.
The second answer choice contains a vague pronoun reference. The pronoun she could refer to Emma or her sister.
The first answer choice shows a possible correction for the vague pronoun reference. She has been replaced with Emma.
Emma and her sister posed for a photograph, but when the flash went off, Emma blinked.