One would really have expected Her Majesty, if summoning everyone of importance to Westcrown for an extended event before they've had any opportunity to secure city homes and staff there, to have made accommodations for them in the palace, but she hasn't. The obvious guess is that it's because it would seem unprincipled to the Galtan archmage to make arrangements for the Archduke of Sirmium and not for a random wretch they dragged in off the streets, never mind that the Archduke has a staff to house and security requirements and will need an entertaining space if he's to accomplish even the most minimal work on Her Majesty's behalf.
Ah well. When the Queen demands that one appear to her Constitutional Convention, one does that with a staff capable of fielding whatever the Constitutional Convention turns into, even if it costs a small fortune. Or a large one. If one has to send to Absalom and pay through the teeth for a wizard willing to cast a Mage's Magnificent Mansion every day -
- well, one has some counties to hand out for precisely this reason, right?
Carlota arranges a Mage's Magnificent Mansion enterable just outside the palace, with a staff on hand to replace her possessions to their expected locations when it inevitably dissolves each midday and is replaced with an identical one. She arranges for what's not required from the mansion's magnificent feast each day to be handed out to the city's poor and desperate, because she's a Good person. And she sets about inviting every person of importance in Cheliax for dinner, so that they can arrive at a common understanding of what to expect from this Convention, and do Her Majesty's noble work all the more diligently. And if anyone else has chosen not to spend so extravagantly as to have a well-appointed entertaining space themselves, well, they're very welcome to make use of hers. She won't even pretend that the walls don't have ears, but presumably no one is here this month for an event hosted by three archmages under the assumption there are walls that don't have ears.