To be fair, it's likely that the author's former friend would have a hard time disagreeing with this if presented in exactly the way that you have.

I suspect that what such a person finds offensive isn't OOP's behavior (i.e. receiving a hair treatment without incident), but rather the thought in and of itself. Since they know that they can't credibly assault a person's character purely on the basis of an involuntary or intrusive thought, they have to settle for calling out some behavior as a stand-in for the thought. In an alternate timeline where OOP had apologized (which would really just be extremely socially awkward, not outwardly harmful), I'd bet on the former friend making the exact opposite stink and chastising OOP for failing to keep it to herself.

Another layer that wouldn't be surprising in this instance would be subconscious homophobia. The friend thinks she's upset at OOP for "victimizing" two poor strangers without their knowledge, but in reality she's disturbed by the sudden realization that she herself may have been or may one day become the unknowing object of such thoughts. Since she can't say as much without implying that she's categorically uncomfortable being around queer women, she reached for any excuse to turn it around on OOP and make herself feel like the good guy.