First - very safe and tender hugs to you!!
Second - some of us here on PC ( me raising hand ) have been in a similar situation with very similar thoughts. At a point when I was just getting in touch with my own sx related issues that were a DIRECT result of CSA, I found myself in a hotel with two men. UGGG! I was in Therapy at the time and had spent a lot of energy trying to teach myself what healthy physical relationships were about. The shame and guilt I held over what happened that day led me to lying about the event to T and almost messing up alot of self work I had done. So my advice is based on my own experience.

Finally, Do as your T says - do NOT beat yourself up over the event. You are in the process of finding a new you. You will sometimes fall back into old patterns of behavior as you are healing. Part of the reason for this is because you may be doing what my old T called "trying them on one last time" :-) When he told me this after I finally came clean on the details of the event, I was so relieved! He said this was natural for people with addictive personalities like mine to do. So I "tried it on" and was not happy at all with how it "felt" or "looked" on me! After I processed through the YUCK UGGGG emotion of that day, I felt very relieved and happy. I saw I was clearly NOT the person I was when those behaviors were a "norm" for me. And you know what? I was glad it happened. Glad because it solidified for me who I had become as a woman. And I LIKED the new me! A whole lot :-)