I probably shouldn't comment on this as I don't have enough experience to know if my interpretation has relevance or validity.
If any of my assumptions or interpretations are off base, disregard this post.
But here goes...
I surprised her and wore lip gloss for the session before she left. The Mistress used my mouth with abandon with me gagging, but I was getting used to it. She began laughing and the Mistress blurted out something I always suspected, but never wanted to admit to. "I'm not laughing WITH you I'm laughing AT you."
I think she misread your reactions to her actions/words/laughter.
To me, the worshiping of a strap on indicates a sign of submission, a fetish, and/or a desire for humiliation.
It seems your incentive was different -- mostly getting pleasure from the fact that you gave her pleasure by submitting to that activity.
I suspect she believed humiliation was the driver, particularly since even after verbally putting you down, you still requested "worshiping her rubber dick."
So when you wore the lip gloss I suspect she felt it was an indication that you were seeking humiliation... and being laughed at is usually very humiliating.
I think her statement was an attempt to titillate, not hurt.
However, her being blind to your motive of just bringing her pleasure was overlooked with disastrous results.
Again, my comments are made in ignorance.
I don't know the personalities of participants nor of the details of the relationship.
Its just that, from your brief post, I get the feeling that a good relationship has been irretrievably compromised over a misunderstanding -- and that saddens me.