If you just told her that you were on chapter six and were hoping she'd take over, that's a bit of a long shot. If you want her help, you need to clearly ask her to help you. Therapists aren't mind readers. Sometimes you have to spell it out for them exactly what you need. If you need her to go through the chapters, reading it out with you, ask her to do that. If you just need to talk to her about things as you read the chapters, ask for that. If you want her to ask how you are doing with it, and offer support, tell her that you want her to check in with you.

It sounds like you guys are on two different pages, her thinking you're fine going through, that whatever triggers are happening are manageable, and you thinking you're in over your head. It's up to you to make it clear, she can't help you unless she knows how bad it is.