Whether or not the nylonase enzyme was generated by a frameshift mutation and resulted in a new protein fold, the fact of the matter is that mutation directed a completely new enzymatic activity!
As I understand their argument, Axe and Gauger claim that new protein folds are exceedingly rare. But this is really part of their long-standing argument that "sure, evolution can work on small scales, but show me something brand new that mutation and selection have done!" I would say that mutations leading to the development and honing of an enzyme (with or without frameshift and protein folds) that breaks down a newly-introduced synthetic product is a pretty good example of evolution doing something new.
I also have a problem with the way she threw the word "nonsense" into the discussion, especially since she misapplied the term (a nonsense mutation is a nucleotide substitution that makes a premature stop codon). It really seems like this is a desperate attempt to divert attention away from something that doesn't fit their narrative.
Thanks, @pevaquark, I'll check out the actual article later (and not Gauger's interpretation of it) to see if there is more to add.
(nice photoshop skills, by the way!)