Fortunately, she did so all in one place, and right while I was watching, so I was able to catch her (priority #1) and contain her in the bathroom (priority #2) before cleaning up the mess before anyone could step in it (priority #3).
She has been announcing her displeasure at being not only sick, but locked in the bathroom, loudly. shammash has been most concerned, and is even now lying on the floor outside my bedroom door, with one paw tucked under the door, to keep an eye on things.
Now that the howling has died down, I think I can maybe go in there and change out her litter (before she threw up, she had some digestive nastiness from the other end) and deliver a bowl of water (versus the toilet, which is her favorite anyway) before leaving her in there for the night.
*Yes, I know cats don't have crops.