A useful attitude/mantra is: "make the stoker happy." So whatever she wants, you bend to it, unless it is unsafe. You are ultimately responsible for any accidents - so blend that responsibility with her lack of control; e.g., if she isn't used to spinning, then go slower for her and work overtime on picking up leg speed with her. The first rides should be mellow, short on Captain attitude and long on fun - so she'll want to return to the tandem over and over.

Both of you might benefit reading stoker posts to learn from that perspective - there's some good ones.