You have to remember that Tom is the unreliable narrator with a victim complex...
Thomas may in fact be the
ultimate unreliable narrator, which is why - in the absence of any physical evidence - the whole story being an allegory for his own "life" [such as it is] makes the most sense.
But that's just my read on it, which I admit could be wrong. So...
so put yourself in the situation as a rational thinking person.
Either the woman saw the writing on the wall and didn't want to have his creeping ass around.
Taking his claims at face value, the woman was already deep into "Sabrina". He's stated "she" [she was a troon, right?] was a twenty-something, so she was already guilty of some form of deviate sexual contact with a minor.
He walks in and, so the story goes, is "invited" in between them; presumably that makes them both open to the event.
It's hard to fathom she either objected to the sharing aspect of the matter
or the fact that "Sabrina" was a minor given her own conduct.
Or
It wasn't his fault, but that young Jezebel who lured him to bed with her feminine charms and thus drew the jealousy of the other woman so she kicks him out instead of the young hussy?
In that case he has to be lying about being "invited" into the scenario, otherwise why not just suggest that "Sabrina" was far more into the idea of bedding both of them than the other "woman"? Wouldn't that serve to further his fantasy about how she was "fully developed" and "mature"?
It would seem that the other party would be upset with
both of them in the second scenario, and throw them
both out - assuming she wasn't so disgusted with the idea of engaging in a three-way she doesn't kick them out before any invitation is offered or
Thomas is in a position to engage in any act with "Sabrina".
Which one makes more sense?
Honestly,
neither. The whole thing sounds like it was concocted by someone less informed on such matters than the
Seinfeld writers.
But, again, that's just my take. We're reasonable people and we can agree to disagree.