I can understand where this fear is coming from, but, honestly, that you have this fear at all shows that you're not likely to body shame her. I think your T will entirely understand that your ED thoughts are about you, and not about her. Now, sometimes our thoughts do extend to thinking about other people (there's a reason 'reverse thinspo' exists), and that is ok too. It's ok to think your thoughts, feel your feelings, and talk about them with your therapist, who is a safe person equipped to handle these things. You can't control this stuff, and she knows that.

What you can control are your actions. You can control whether you attack her about her weight (and I really doubt you ever would!). Body shaming isn't the same thing as talking about your ED. I promise.