Quasebarth: The best way to me seems to figure out why her computer is not showing up. I think the easiest solution would be to establish a home network group which automatically handles most common shareable folder. Details see here:
http://windows.microsoft.com/en-us/windows-8/homegroup-from-start-to-finish It should work with Windows 7 as well, but I don't know for older Windows. I think the Homegroup system was introduced with Vista.
From my experience with such situations (had similar problems with Windows Vista and 7 in my network) it usually boils down to user rights and user network accounts. Whether you have to create all the same users to have access to every PC in the network or you work it out with the generic guest login. The guest login however is very restricted what it can do and see, and on top of that is sometimes disabled by default which makes working in the network a bit strange. Cleaner solution is certainly to have the user logins that operate in a network on every PC of the network.
The Homegroup system will circumvent this hassle altogether though which is why I would suggest it as a preferred solution.
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Thanks, I was avoiding the HomeGroup option because I did not know it was avaialble in Vista as well.
I'll try Homegroup first and then go for BitTorrent Sync as a last resort.
BTW, on again - This is Win 8.1 64-bit to Vista 32-bit