Child Visitation During Sickness

My question involves a child custody case from the State of: California

This past weekend my son went to visit his dad for his visitation weekend. He has been fighting a cold. I was pretty sure he was getting over the cold and did not even think of rescheduling the visitation. In the past when he has been ill we have just rescheduled for the following weekend. It is my view that the non-custodial also must share in the care of a sick child. Anyways, yesterday I received an email for the first time ever from my Ex's pregnant girlfriend. She was very angry with me for sending them a sick child and now she is sick with the same cold. I am bothered that I have to worry about sending my son to spend time with his dad around the girlfriend. From the tone of the email I get the impression that she really does not care about our son. I am not sure how to deal with this concerning my Ex. I also have the cold and I don't get breaks when I am sick, it is just part of parenting as far as I am concerned. Our son is almost 15 years old. The other part of this equation is my Ex and his girlfriend are moving to Austria in late October for an extended stay of 7 months. I would assume that my Ex would want to spend time with his son because of this. I am not even sure if my Ex knows that his girlfriend sent me the email. I think it is totally inappropriate that she contact me concerning the care of my son and that it is just between his father and I. On top of all of this my son is upset that his father is moving. My boyfriend and I just told him that we weren't going anywhere and would always be there for him.