carring clients

Hello, I need help please; my partner is a career, which means she travels to different clients each day. The issue I have is that sometimes she is asked to take the clients out, could be to the shops or to the seaside, using her own car. My partner has business insurance but we are not sure if the client is covered to be carried in the car. We have spoken to our agent and believe it or not they don’t know either, can someone help me please.
Many thanks
Baldric