But he says it's fine if they interact for short periods of time since they will be living together...
I have to disagree. They should not be around each other at all for 3 weeks. If she has something and it is airborn, then it doesn't matter if they are around each other for 2 minutes or 2 hours. Please rethink allowing them to be together for any length of time.
I am glad she will be with someone who will care for her while she goes through this pregnancy.