I would try to amend my own thinking and wording from "upset with me" to "giving me her thoughts and feelings on the subject". She could have been like you and not shared with you how your behavior impacted her. I would stay with that positive, that she cares enough to let you know and think about what she actually had to say, rather than how you feel/perceive it.

I can get really tangled if I mix up my actions (sending/not sending negative emails) with how I feel and give my feelings priority over everything else. Feelings are to inform us, like our thoughts are, not goad us into action on their behalf.

Your thoughts and feelings are yours but your actions belong to all those around you, are public, especially if they are actions one-on-one with another. The thoughts and feelings are just backups to help us decide how to act, they should not be used alone for determining our action.

It is your perception that your T is upset with you. You should ask her if she is upset, check out your perception and/or decide if there is "cause" for her to be upset (and thus your perception could be correct for your own intents and purposes) and then fix the problem, not worry about your feelings.

The feelings just let you know there's a practical problem somewhere, they are not the problem themselves. If you feel lost because you feel your T is upset with you; work on your behavior causing her to be upset with you and the lost feeling will probably go away.