Amy seems to be using "that" (in English) and "das" (in German) as a kind of definite article, as in "you that daddy frog" (you are the daddy frog) / "du das Mami Frosch" (you are the mummy frog).
(And I think that her German "das" is the demonstrative-used-as-definite-article, rather than the homophonous German definite article "das", since where she previously had definite articles, it tended to be uniformly "die" -- as in "Das - die Daumen, das - schüttelt Pflaumen, das - heb' auf, das - bringt nach Haus, und das - alle auf!".)
Reminds me of how Romance definite articles derived from Latin demonstratives.
Ontology recapitulates phylogeny, or what was it called. I swear Amy is going through centuries of grammatical changes and innovations in dozens of languages, all in two years.