Sometimes you just need to go with your gut, I think.
FL_GirlByProxy said something important. This was the only letter bmom intended/intends to write for dd (at least for now), despite our ongoing exchange of pictures and updates. And when you look back at what you've written years later things don't seem nearly so important as they seemed at the time.
Bmom wrote the letter after having just begun counseling. We also had extensive heart to heart talks at the hospital and have corresponded since. She consistently says she wants us to do what we think is best for dd and just make sure she knows she was loved and cherished at birth. In fact, the letter bmom originally wrote for dd before she was born was substantially revised to include less detail by the time it was emailed to us. For that reason alone, I don't want to ask her to rewrite it. It's hard enough the first time.
The letter really needs to be as clear a statement of her feelings at that time. With revision comes changed insight.
Plus, there are really just two sentences, phrases, that seem overly detailed. So - my thinking is that I'll redact those two phrases (which she won't know are missing - it's a Word file) and keep both versions of the letter, edited and unedited. When the time comes dd can have access to both if she chooses.