First, to answer your question "if your T has disagreed with a previous provider how have you handled it??", I think, you might've meant if "your T agreed" ?? because that's what flows logically from your description of how your emdr T agreed with your other T.

In any case, I never saw two Ts at the same time, and when I ended the work with one and moved to the other one, whatever problems I had with the previous T, the current T seemed to "take my side", so that was never an issue.

Now, in terms of your situation, I can't not to comment on your T insistence to break off contact with your brother. I understand from your description that your brother's behavior around underage girls may be more than just inappropriate. What I don't understand is why your T isn't just reporting it to the authorities if she believes that something is going on that deserves reporting? Why did she tell you that she'd have to report it IF you don't cut ties with him? What does reporting have to do with you having or not having a relationship with your brother?

She is a mandated reporter, as all therapists are. If she believes that your brother is sexually abusing minors, she is legally obligated to report it REGARDLESS of whether you have a relationship with your brother or not. Why is she making her reporting responsibility dependent on your continuous contact with your brother?

It is not her place, as a therapist, to advice you on a status of your relationship with anyone and, it is certainly not her place to DEMAND that you cut ties with someone for whatever reason. She has to follow her legal and ethical obligation to report regardless of your personal choices in regards to your brother.

And saying to you that she'd have to close her practice and relinquish her license if your brother did anything to your daughter is just a bunch of horseshit. She has nothing to fear if she reports what she is mandated to report (again, if she has a reason to believe that it is reportable).

I understand emotional reactions people have towards the behavior your brother displays, but, when someone is a professional, they have to deal with it professionally. I don't see your T behaving professionally in this situation. Besides, if she knows the details that require reporting and she didn't report them to the appropriate authorities, then she is also breaking the law.