She isn't! She shouldn't even try to explain all of this on the Queen's expensive time; after this, Keltham can get an emergency one-hour lesson in how to interact with a non-incognito Queen without that being an Incident if it happens in front of her advisors. Even then, if he suddenly hears Isidre's voice magically whispering in his ear, he needs to immediately pause whatever he's doing and listen and not argue.
(This will give Carissa Sevar slightly more time to recover; since, it has by now been reported to Abrogail, the cute little idiot went and submitted herself to her any-time-in-three-days torture session right away, without making sure it happened sometime when she'd have an hour or two to herself to recover afterward. Was Sevar that stupid, that overconfident of her recovery ability, or had she just never previously gotten herself in important-project-screwup, mentally-insubordinate-to-the-Queen levels of trouble? Probably all three.
It is infuriating that the child has gotten herself into a vital position where she needs to be accommodated for incompetence like that, rather than it being turned into a more object lesson. But they're planning to try out Lrilatha running Suggestion on Keltham; and while that is expected to go well, Sevar needs to be in better form to exploit whatever change Keltham has then in his thoughts.)