Topic: 1 NNID - 1 System Limitation

My GF finally made her own profile on my WiiU due to Captain Toad not featuring multiple save files.
She said, that the system told her, that she will be only able to register her NNID on a single WiiU.

The question now is: Does that mean a single WiiU entirely, or a single one at a time ?
SHes planning on getting her own system once her finances allow it. So i got curious: If we delete her profile from my system, will she be able to log onto a new one ? Save files are not an issue, so dont care about those

I would recommend that she doesn't make a NNID until she has a system of her own, however if she does make one you should be able to contact Nintendo to get it transferred.

She doesn't need to make an NNID to play on a separate profile, only if she wishes to play online and/or use Miiverse. However, she can always make a secondary one with the intent to make a primary one on her own console (I add different letters/numbers to ACK). The only real issue is that eShop purchases will be linked to whichever account was used to purchase. As long as she doesn't buy eShop games there will be little impact whether she makes one or not.

From personal experience, it is possible to transfer a single NNID from one Wii U to another, but it requires a phone call to Nintendo and having both the source and target Wii U's serial number.