When do actors become self-employed?

I have a new client is on the edge of becoming well known. She appears in increasingly high-profile films as one of the leads, and commands good money for doing so. My question is whether she can claim to be self-employed and therefore bill for her services through a company without risking falling fowl of IR35 legislation. I have spent the day reading up on the web, and I have spoken to the HMRC film industry unit (who have offered to pre-approve her latest contract), but in the meantime, I would be grateful for any views that are out there. Many thanks in advance.