What is the endgame here?
It’s quite possible that what Ms Chandauka wanted was to have the governance issues at Sentabale investigated by the appropriate regulatory body. Then she took steps to preserve her own position after the Board tried to dismiss her (which is illegal if she is classified as a whistleblower, remember, and something that could properly found a claim for an injunction to prevent it).Then, faced with concerted public action by the Board and patrons to undermine her, decided to fight back rather than roll over.
If Harry and the Board had genuine concerns about her behaviour, presumably it would have been better to let the charity commission investigate (assuming they have nothing to hide) and then go through a formal and proper process to dismiss her when the investigation was concluded with either no findings, or with findings against Ms Chandauka. Trying to sack her when she could claim to be a whistleblower was a bad option (did they not take advice?) and all resigning in concert was a nuclear option.