Have you considered that you D12's anxiety may be caused to some extent by what is not being said? What I mean is that she sees what's going on and no matter how "normal" we think we are being...we aren't. This is all very stressful.
Your daughter more likely than not, understands more than you think she does. Regardless of what she understands, she can "feel" that things are amiss. Consider that the lesson she learns may be to not trust her intuition/instincts.
I understand what you are trying to convey in your letter. I don't think it will be taken the way you intend. Just my 2 cents.
