Being told by a therapist that you have trauma that you don’t remember at all AND that this trauma for sure relates to one specific person whom the therapist has identified AND that this trauma is the entire explanation for your current problems sounds like incompetent and unethical therapy.

I would be worried too.

Even if this therapist happens to be correct about a history of abuse perpetrated by this person’s father, and furthermore about its impact on your friend, that’s still not an ethical or appropriate way to approach it.