Autumn: would it be possible to say she is injured later in the day after the fire breaks out? Smoke inhalation perhaps? She could always hit her head or something on the way down from passing out from the smoke. That way not everyone is getting injured at the bridge or getting supplies. She will need someone to find her though when she doesn't come back or while they're out collecting supplies.
Isabella: has taken up residence in the Vaults and has taken it upon herself to look after people there the best she can since she can't fight monsters. She will be making tea and bringing it to people and if people can't find supplies she'll share what she has. Other than that she is just kind of in a daze over the whole thing and it almost doesn't feel real but mostly she is alright because she hasn't lost anyone she's close to and she just arrived not too long ago.
Fleur: will be out walking around most of the day to make sure there are no more monsters lurking around because she feels it is what she can do to help. She will be in and out of the vaults too because as the long time bank manager know one knows the vaults like she does. When Victoire dies she's going to be there and once that happens she will be about useless. She will want to just go find some dark spot far away from everyone else (outside most likely as long we she stand the heat) and just cry. She's not the type that likes to cry or fall apart in front of people though if she's close to your character she won't mind as much and they are more than welcome to find her hiding spot.