If she decided to leave, then it should be fine as China doesn't care your visa to Canada expiring or not. However, if her visa expires now and she doesn't do the health checkup as required by Canada immigration, then next time, she may have trouble when coming to Canada again. She could be stopped at Vancouver by Canada immigration officials asking her why she didn't have the health checkup done last time and they have the right to send her back to China immediatelly.
BTW, Canada doesn't check the visa if you leave Canada, so won't have problem for her leave. But may have problem when she come back again, unless, she will never come to Canada again.