Re: killing the hardiest of plants
When you say that it is right below a misting nozzle, does that mean it is in one of the wettest parts of the vivarium? Most ferns, while they like light moisture, demand very well drained conditions to keep their feet dry. They hate wet roots.
I've not kept rabbits foot ferns, as I like them tiny. A quick search brings this up, "The Davallia fejeensis belongs to a genus of 40 plants that are epiphytic in nature, which means they grow on trees or within rock crevices taking moisture and nutrients from other sources "not soil" such as air, rain, trees and other debris."
Epiphyte. Epiphytes in general, hate wet feet. They grow in trees, or in rock crevices, in very little to no "soil" or substrate.
I think she might well be telling you that she has jungle rot so bad that she's having trouble walking, and needs a new pair of dry boots.
Questions are not ignorance. Questions are the birth of knowledge.