I agree with Kyle. If I may add something, I would say that in this scenario, the PM decides that the communications management plan is outdated, so a mere update would not be enough. She needs to go back to planning to revise the communication mgmt plan completely.
For sure, the communication mgmt plan may be updated as a result of the Manage Communications process. But keep in mind that those are components that MAY be updated, including but not limited to those listed.
As a final recommendation, I encourage you to use the Live Feedback option available in the simulator when you judge the explanation provided as inadequate.