In this sentence she gets depressed/disappointed when she says the last sentence or just the last words?


In the sentence 最後の言葉の時だけほんの少し俯いたけど when she says she got depressed or
disappointed, it refers to how many words of the last sentence she said (or
maybe the whole sentence as she had said 3 long sentences in a row).




Generally, when someone is emotionally affected by 最後の言葉, it means not the
exact the last word, but the last whole sentence or some of last sentences
which convey one meaningful content.

We use the similar expression like this as

> 結婚式{けっこんしき}で新婦{しんぷ}はお父{とう}さんの **最後{さいご}の言葉{ことば}**
> ‌の時{とき}だけ少{すこ}し涙{なみだ}が出{で}た.

In this case general translation will be like;

> The bride cried a little only at **the last part of her father's speech** at
> the wedding ceremony.




Generally, when someone is emotionally affected by 最後の言葉, it means not the
exact the last word, but the last whole sentence or some of last sentences
which convey one meaningful content.

We use the similar expression like this as

> 結婚式{けっこんしき}で新婦{しんぷ}はお父{とう}さんの **最後{さいご}の言葉{ことば}**
> ‌の時{とき}だけ少{すこ}し涙{なみだ}が出{で}た.

In this case general translation will be like;

> The bride cried a little only at **the last part of her father's speech** at
> the wedding ceremony.

