Read it over again. Alisaie is getting their names wrong because she can't tell them apart.

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Alisaie: So near and yet so far... Well, it avails us naught to stand here and stare at the thing. Let us away to Mor Dhona, and try the other fragment. Perhaps Sinis has fared better. (She is in fact talking to Sinis.)

Alisaie's Assistant: Ah! U-Upon that note, my lady, there is something I must tell you. I am sorry to report that I lost contact with my brother just over a bell ago...
Alisaie's Assistant: A-As you know, the Singing Shards are home to many fell creatures, ogres among them... While I do not wish to cause you undue alarm, I fear something unspeakable may have happened to Deks. (He refers to Deks by name to make it clear that it's not him, without actually having to correct his boss.)

Alisaie: What!? Why didn't you─!? Give me strength! (She has caught on and is horrified she's been getting it wrong. "Why didn't you say something sooner?" is most likely the intended sentence.)