BBK,
All of us wish we could undo some of our parenting decisions, but all of us did the best we could at the time. As we learned more, we did do better. I would tell the therapist about both incidents as well as your instinct that something happened or she saw something when she was with her dad. She or her friend may have also seen things on tv and be acting them out without full understanding of it.
You are a great mom for Tink. I think if it gets to the point that she needs Residential Treatment Center (RTC), you will help her get it. But I also think you will know when it is time.
Can Copper babysit next weekend? It sounds like you need time to recharge your batteries.