StupendousMan wrote: ↑Thu Dec 05, 2019 12:32 pmSpoilerShowA better way to think of this phrase is that the Japanese adjective is "taisetsuna", and Erika wishes to use the informal form of the verb "to be", which is "da". If one simply puts the two words next to each other, one would get "taisetsuna da", but that combination grates on the Japanese ear. In cases such as this, Japanese speakers add a terminal "n" to the adjective, so that the phrase becomes "taisetsunan da".
Google Translate is going with the colloquial "nanda" from "nani desu ka" (what is it?). The difference between the two is in context and intonation, and...sometimes...question marks in text. Of course, GT has no idea about any of that as it's using statistics to translate, so its input up to now probably has a higher rate of the question form.