Multi-monitor virtualisation with Parallels Is it possible to make a Windows 8.1 VM running on Parallels think it has two monitors but in reality these monitors are just two separate "desktops" as far as OSX is concerned running on a single real monitor?
I don't think so - even in Coherence mode, which would allow you to place different Windows apps on different spaces, they have a tendency to overlap each other, depending on which was actually last in front.

I think you might have to try using Sysinternals (Microsoft) own Desktops v2 tool - which I haven't tested in Parallels - but this guide may help - Unlock Virtual Desktops on Windows 7 or 8 With This Microsoft Tool