Interestingly, Amy uses /d/ for voiced "th".
I find it interesting because Germans tend to use /z/ instead, whereas (as far as I know) native English-speaking young children tend to use /d/, like Amy. (Apparently, both "th" sounds tend to be acquired comparatively late even by native speakers.)
I also find it strangely gratifying that this means she's speaking "normally": toddler-accented English rather than German-accented English. (Though she probably has German influences in some other aspects of her pronunciation of English.)