As a woman, here’s what I think likely happened with Katie/Left4Dead based on what we’ve seen so far: she had a couple of hookups with Tom that went over relatively well for the most part, possibly some unsavory behavior but nothing enough to keep her from messaging him after to try and pursue meeting a third time. When she pressed him on a potentially more serious relationship, as she likely caught feelings, he was honest and told her that he wasn’t looking for that at the moment, and that’s a no-go for women with emotional investment, especially one of the BPD nature. Tom took on a much more sour image in Katie’s mind because of his rejection, and when given the opportunity to drag his image through the mud, she was glad to oblige.
But that’s just my opinion.
This makes the most sense to me.
I don't know about the full blown armchair diagnoses of BPD but "rejection sensitivity" is a core aspect of it:
https://www.sciencedirect.com/science/article/abs/pii/S0165178118303081
Not only that, BPD people can't deal with any form of ambiguity when it comes to relationships. I would guess they adopt extreme black and white thinking when it comes to this so as soon as he said, did or emotionally showed anything that wasn't 100% "I am attracted to you and you alone and want to spend time with you and have sex with you" they lose their shit:
A sample of 256 young adults completed self-report questionnaires assessing rejection sensitivity, effortful control, intolerance of ambiguity, and BPD features. Results showed that effortful control and intolerance of ambiguity mediated the association between rejection sensitivity and BPD features. The present study showed the role of cognitive aspects including both effortful control and intolerance of ambiguity in the relationship between rejection sensitivity and BPD features.
"Rejection sensitivity" is quite a strong insignificantly documented aspect of ADHD also (not bullshit ADHD just so you can get meds to study/work easier but people who actually have it) and there are some off-label blood pressure medications that can help to deal with it.
Even if these bitches don't have actual BPD (it is rare) it is not beyond the pale that this was one of their first significant relationships and Turkey Tom was considered a "celebrity" (so any form of rationality went out the window long ago) who had multiple women vying for his attention and the very loud emotions involved in dealing with something like this was something they just didn't know how to handle.
I firmly believe these kind of communication and emotional difficulties with interpersonal relationships (platonic, romantic, sensual or purely physical) are quite common and because faggots are all addicted to TikTok they're not sexually experimenting or hooking up or having playful flirting with that guy in the office as much as they used to, so these important personal development milestones are happening much later in life when in reality they should've experienced this kind of shit when they were 13 years old (Turkey Tom included in that).
I think on top of this so many "modern people" in the smartphone era have this idea of relationships that is fundamentally incompatible with IRL/real life relationships. On the internet you can instantly block or browse past people you don't like. It is common for people to ghost others. Most talking is done via text messages which cannot convey emotions or timing properly and the lack of nuance can cause real problems with the development of relationships and consequently the emotional development of young adults.
Even though taking screenshots and saving dossiers of people you're in a relationship with is not new - it is not really a normal, healthy habit. I know this because it has some parallels to how I acted when I was a young adult. If you're in a relationship where you need to screencap shit then you shouldn't be in it. You shouldn't be looking at text messages from people and building conspiracies in your head that they're ignoring you or cheating on you or anything like that.
And if you do then you should go work on yourself before getting into relationships because if you're not semi-stable and mentally/emotionally healthy enough personally then any relationship you get into is 95% likely to be with someone who is just as broken as you are and it will be a shitfighting disaster.