Is It Advisable To Meet An Infant With Fever Blisters?

I have a 7 week old. I know they have low immune systems so we are trying to keep her away from as much germ/possibility of illness as possible esp til she gets past the 3 month mark. My mother in law was supposed to fly here to visit us on Monday. She has been sick on and off this past week with fever/cough symptoms and taking meds (not sure what) and has felt better the past day or two. She woke up today with a fever blister. Should she reschedule her visit?