Hi,
Sorry I don't know your full story, but I can only think of posting this. For me - its just a case of simply being you, and letting time heal whatever rift has developed. It sounds to me as if Erin needs to learn to trust again and rebuilding trust takes time. There is no magic fix. You mention a letter, how about writing another one, this time explaining why you wrote the first, but how it was wrong. Words do impact, and unfortunately as often as we would love to take something we might have said back, we can't.
As I've said, it sounds as if time is going to be the biggest healer here. Time to rebuild. Time to show trust again. And so patience is also important.
I really hope this works out for you.