Quoting Layla-and-Faith:" NOT true!! Preemies are much more likely to become deadly ill if exposed to illnesses that may seem ... [snip!] ... My preemies lungs collapsed from being sick.. I can't stress enough how important it is to keep baby away from sick people."
Okay. First of all... I misunderstood. I didn't realize her SO's daughter was already sick. I misread.
But regardless... if his child WASN'T sick she is fine to be around the preemie if she was discharged and brought home. I understand that they are a lot more fragile but honestly, you don't ship your other kids away when you bring a preemie home. That is still his daughter who needs to meet her sister and be with her Daddy... of course, when she is better.