The first question is ""which Windows emulation?"". I use VMWare Fusion on my Mac and there is little or no problem with it. Other than keyboard differences, it acts just like Windows (except it tends to be more stable than my old Windows laptop). VMWare Fusion hosts virtual machines and those virtual machines look just like real Windows machines to the applications.
One thing that can cause problems is how they are using Fusion. One of the options is to run in Unity mode, which will allow you to run a single Windows app almost as if it were a Mac app, in it's own Mac window. I think you could have problems trying to use that. I like Unity mode, but I don't like the fact that some apps have issues with it, so I don't use it. If they're trying to use it that way, it could cause a problem, I think. I usually start Fusion as a ""single window"" with a Windows desktop.