Bear in mind that we're reading a comic in which a trollified horse, for instance, can survive ninety years tied up and therefore with effectively no access to food or water. I suppose it got rained on from time to time, but that's hardly going to have been enough to keep a physical horse hydrated, let alone fed; and yet, there was still a physical horse there.
While the details are unclear to us (and I suspect may also be unclear to Minna), I think we have to assume that magic, in the SSSS universe, is capable of overriding physical constraints.