A girl constantly controls the group because she fears a decision will be made in her absence.
In the example, uncertainty also arises from an organizational rule: appointments change without summary. I propose to solve that problem first, asking for a final message with place and time.
Reducing the ambiguity of the group may be more helpful than reprimanding the individual for each check. If concern continues in many contexts, it deserves listening without being trivialized as a digital whim.