You need to decide what outcome you would like from this.
If you want to keep her as a client, I would suggest doing nothing. The letter is a pretty clear indication that she likes to be right, so you making her wrong won't help very much.
If it's important to you to make a point, send the information. The likely outcome is a continuation of the dialogue and losing the client.
The important thing to remember is that you diagnosed correctly, treated it correctly and observed the customers wishes. There isn't anything more you could have done.
Mike
If you want to keep her as a client, I would suggest doing nothing. The letter is a pretty clear indication that she likes to be right, so you making her wrong won't help very much.
If it's important to you to make a point, send the information. The likely outcome is a continuation of the dialogue and losing the client.
The important thing to remember is that you diagnosed correctly, treated it correctly and observed the customers wishes. There isn't anything more you could have done.
Mike