D.W.
Has she been diagnosed with an upper-respiratory illness or is she assuming that's what it is? If she's being treated on antibiotics, she should be OK in a few days - you may want to ask what the specific diagnosis is to see if she is contagious or not (not all infections are contagious - such as ear infections).
18 months ago, I was diagnosed with cancer and literally had NO immune system. There were times my blood was drawn and I had no white blood cells. I had a 2 year old and an infant (she was 10.5 weeks at diagnosis) both in day care full time, and my job was to go in and out of doctor's offices all day.
My oncologists recommended diligent hand washing. That, hand sanitizer and sensibility (not sharing foods, kissing directly on the mouth - my kids, not random people) helped keep me infection free.
It sounds like there are other issues (we all have them). But, I'd not be so concerned until you know exactly what her diagnosis is, how it's being treated and whether it could impact your health and your family's health.
I know my response isn't going to be popular, but it's based upon a situation in which infection literally could have killed me, and I came through it OK.
Best wishes.