The quote from her email:
So that part was definitely said on the day Kyron disappeared.
(and this to me has always been suspicious. if you have a back and forth conversation with someone, and the next day you hear on the news that they thought you said you were going to the doctor, how the heck would you know which sentence/part of the conversation they were mistaking for "doctor's appointment"? And why would you assume it was the part where you said 'exhibits'?)
I think Terri also mentioned the appointment before that because there was a form involved that the teacher had to fill out for the doctor, and there was talk of "Friday" being the day of the appointment:
From
http://www.katu.com/news/local/100323934.html:
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So the June 4 conversation was the "misheard" one (because she's new, and has a bad ear) and the earlier misunderstanding was about which friday it was. So Terri says there were two misunderstandings by the same teacher. One mistaking exhibits for doctors, one mistaking one friday for another.