The post I've just shared explains a (little) bit about being a trustee. The concept of Sophie Chandauka self-reporting to the regulator if she has been guilty of wrong-doing, is possible. But would be an insane move from someone who by all accounts is well-educated, legally trained, and experienced in governance and corporate management.
A trustee who believes in the charity's mission, wants to stay involved and is confident of their own accountability and transparency, should not feel the need to step down. A trustee that has been party to less than transparent dealings, either actively or passively, would be far more likely to want to head for the emergency exit. The irony being that it won't matter a jot in respect of their liability because that ship has already sailed.
The acid test here is whether you are able to recruit new trustees with the skills and experience you need. The fact that Iain Rawlinson has agreed to join is very telling. He is a very experienced trustee and non-executive director. It's extremely unlikely he would have joined as a trustee unless he was confident in the charity's direction and Sophie Chandauka's actions.