Unfortunately, members here are not allowed to diagnose, even if it is obvious. However, since you are in a dissociative forum, we can assume you have ideas about the cause. I will say this: I have been diagnosed with DID and have had other psychiatrists and therapists rule out DID in our first meeting after reviewing my history and seeing that I have previously been diagnosed with it. Sometimes without even seeing me first (as evidenced by the date on their notes). The only way that can occur is that they staunchly refuse to acknowledge the existence of DID. Many mental health practitioners fall into this category and so... the fact that her therapist is stumped doesn't surprise me. If you're losing weight rapidly and no physical disorders can be found to explain it, and your therapist doesn't believe in anorexia (or eating disorders in general)...well, you might see where they could become stumped.

The above was mentioned as more of a cautionary tale based on a clumsy attempt to read between your lines, not an attempt at a diagnosis. I would just prefer finding a mental health practitioner who is not going to come to the table with a set of limiting ideas about the cause. If you have any choice in who she sees, I would suggest someone who is trauma informed at the very least. You're both smarter than the average bear (old cartoon reference) - use that and don't follow another's biases blindly. Trust your gut and know that my PM box is open to you.