Is it ok for my 4 year old to be sick around her baby sister?

So my daughters father & I have 50/50 custody and she just started the week with him yesterday. By the time she gets back her baby sister should be here (getting induced on the 20th) and I was wondering if she’s sick (she usually gets sick at her dads) would it be best for her dad to keep her until she’s better? or is that not necessary