If she went 3 full calendar months without health insurance, yes, she is subject to the penalty unless she qualifies for an exemption.  There is no exemption for changing jobs.

https://www.healthcare.gov/health-coverage-exemptions/forms-how-to-apply/

However, one day of insurance in a month is considered an 'insured' month.  So the penalty only applies if she did not have health insurance for 3 full months on the calendar.  For example, let's say she had insurance on July 1st, but lost it on July 2nd.  As long as she had insurance by October 31st, she would not have a penalty (only August and September were uninsured months).