Clara will stay (or will try to, anyway). She's going to be hurting herself in exploring the terrain a couple of days before so either someone she has relatively decent CR with can convince her to stay behind or she'll be sensible and suggest it herself. She'll be wanting to catch a trilobite or three just to examine them, to try and get any information of her own to share when the others come back. If she feels she's not finding out anything or becomes too restless, she'll be eager to try and strike out to catch up to the others who left to investigate. A bad life choice but she doesn't do well feeling like she's not contributing somehow.