sullied;

welcome to the forum in spite of the motivation.

My commentary:

I think your feelings may stem from lack of faith in your ability or experience or both. I see you refer to this person as a friend. a few phrases you wrote however triggered something. I see jealous and or pride and the resulting negligence from these emotions on your part.

the key phrases I see are phrases like:
"I've tried to convince myself that my friend in the scene did not fly"
"So what I've found is someone who is my lover, my slave, and also to a certain extent my teacher"
"she thought of being topped by the party host and what the differences were between me and him"
"I was glad to hear that I am a better top then the fellow at the party and she enjoys being with me much more."

I believe these are the foundations of your primary and secondary emotions, and the outcome of these emotions.
The next part that I find interesting is your first statement that you are a Dominant and she is a bottom (even if more experienced then you) You did also offer yourself up for penece, this makes me question if you are a Dominant or a switch. Not that it is a negative that you are, but it does raise the question.

The next point on that topic is to hold the tool and use it or the desire to use it doesn't make you dominant. Sadist maybe. But do you Top for the pleasure of the bottom? If so maybe you should reflect on what I said.

If you did not feel up to sceneing, why? was it fear of your ability? fear of being watched? Where you drinking before the party? Was your arm sore? where you just not in the right head space?

Public scening, especially for a self proclaimed egoist, is a daunting task and a challange to say the least. You expect perfection of yourself yet you know you are not at that point yet, you felt pressured to scene for her sake yet and did not feel adequate to the task.

If your friend was yours at the party, the one that asked you for permission and the one you referred to as "my lover, my slave" Have you spoken about sceneing with other people?

I have a few other points and questions on the topic. But I will leave them and see your reply first.