I've emailed my new t a couple times (primarily ironing out some administrative type stuff) and he seems to do his email mornings when he gets to work. He may also do it at the end of the day; I'm a morning person so I wouldn't know. If his clients need to reach him immediately they (we) would call him. It could be this therapist does something similar. The best way to find out her email policy would be to ask her when she gets back to you and then decide if its something you could live with.