wow. so the principal refused to even consider your childs disability in classroom placement and said her disability is her problem to "get over". Did you get this meeting on tape?
Basically he is refusing to provide FAPE and blaming your DD for her disability.
Have you talked to the school super?
So since they have said that your daughter needs to get over her problem and they are offereing a solution ( sort of) i think you do have to go along with them and see what they plan. But you can ask that the program of desensitazation be evidence-based and put together and over seen by an expert with experience in working with children with anxiety disorders and PTSD. ( this is not the sped head but a credentialed professional in the mental health field with expertise in your DDs area of disability that limits her access to FAPE) If they cannot provide this then you have to consider whether you have evidence that based on the principle's statements that he cannot provide an appropriate classroom to meet your childs needs so she can have access to FAPE, you could have grouds for unilateral OOD placement at district expense.
