Idhris is reading in the Conclave's library while her mother is busy with the council. This is fairly normal for the circumstances - today is not a school day, she has no father, and her mother is unwilling to leave her with the Bosmer servants when the meeting is intended to be short. Idhris doesn't mind busying herself in the Conclave's massive collection in the meantime, so Lady Arannelya just brings her along.
Today she is reading about the legend of Talos of Atmora, or Tiber Septim. The tome in question is not easily available outside the Conclave, she knows, as she had never seen it before. It's easy to see why, as well - the book is rife with the lies of Men, suggesting that the bloody conqueror was favoured by Akatosh - the human name for Auri-El - and insisting that he ascended to godhood upon his death. It's outrageous! But it is also most likely the type of lie the people of Tamriel believe, and therefore a good idea for a future leader of the Aldmeri Dominion to know it.
Besides the ridiculous lies, the book also contains a number of words in the dragon tongue, as it's well known that the Septims could speak it. She mouths the words as she reads them, but doesn't speak aloud for fear of alerting the archivists to her reading material.
Eventually her mother arrives to pick her up. They have a lovely dinner at one of the restaraunts at the waterfront and then return home. Idhris vanishes out into the grounds of the estate as soon as possible.
There's a shrine to Auri-El on their property, as well as shrines to the other seven divines. Faendal says there used to be one to Talos, too, for the human servants who worked for the House of Aldmeri before they were sent back to Tamriel where they belong. Curious, after her reading earlier that day, Idhris goes looking for it.