Just one more viewpoint from a fellow CSA survivor...Obsessive thoughts happen because we try to combat them with denial and moral "I would never". I used to have all kinds of obsessive thoughts about hurting people, hurting myself, etc; but when my T had me talk about the thoughts and experience the full gamut of emotions and consequences that went with them, my brain was finally able to process whatever the rumination was trying to process, and the thoughts gradually tapered off. I had to become comfortable with the painful and uncomfortable thoughts and emotions before the obsession would stop. I still tend to have the occasional "what if I" moments, but because of the techniques my T used to face the truth behind the obsessions, I not only know I won't act on them, but I recognize them as just trauma-based thoughts. While I agree your T needed a more stable base of trust to do such work, therapeutically speaking, this is a rock-solid technique for dealing with obsessive thoughts of this nature. I think she just jumped the gun with you. The trust groundwork hadn't been properly laid for this technique.
Hope you two work this out, and you find relief from your thoughts. It takes time, but trust the process and your guide in it (T) as best you can.