Do you often feel suspicious of people's motives? IIRC, you and your other therapist have discussed DID quite a bit, so the book seems relevant. But don't feel pressured to buy it if you think it's poorly written. I can't imagine that the royalties from a book could be much of a motivator. You buying the book would only enrich her by a few dollors. Instead, I suspect it is that she thinks her book will give you the common language she uses to discuss these issues, like an aid for communication.

To me her suggestions seem quite practical and oriented towards helping you improve certain aspects of your life. Since you live in a group home and don't have a lot of resources, this seems appropriate to me. Wanting to learn if you have ADD and improve your health by writing to your doc seem like good things to me. So does you going twice/week to make more progress.

It seems like all of these things could potentially help you, why not give them a try before you reject them? I don't see what you have to lose, except your skepticism.