In your opinion, what has she said or done here that would prevent her from having a career in cybersecurity?
I've always been told that anyone who feels like they might ever need a TS clearance should hope for the best but assume the worst. There are obviously a few things that will immediately disqualify you, but there's also a requirement that the applicant be "of good moral character", which is usually a way of granting decision makers discretion on what they consider inappropriate or concerning. Applicants who get denied don't always know why, because anyone with serious, glaring issues usually won't get very far if they're even dumb enough to apply. If you have to ask whether something might be a problem, then you shouldn't do it even if you reach the conclusion that it wouldn't be a problem for a normal employer.
As far as her posts here go, the biggest problem is probably going to be the fact that they exist at all. Affiliation with controversial or suspicious groups is one of the hardest things to talk your way out of, and usually gets a hard denial unless there are serious extenuating circumstances. Beyond that, though, you really don't want to be taking your arguments or drama online, and anything that could be seen as racially or religiously offensive is a bad idea regardless of context. She's going on a forum that she claims to know is being monitored, getting into back and forth arguments about a shitty relationship that ended ten years ago, and calling herself and other people "niggas". Maybe she can talk her way out of that, but there are people who've been denied who claim they can't even think of anything that
might have caused it. In this case, it would be pretty fucking obvious. Tarl doxxing her is something that she could probably have worked around, given that he's not exactly got a great history, but choosing to get involved is harder to justify. Some of the things she's chosen to share, like seeing the genitals of one of her ex's other exes, are just mindboggling.
Whether being gay or trans is going to be taken into consideration is a hotbutton political issue and is probably a matter of official policy, where evaluators aren't given that same degree of discretion. It doesn't really say much about how difficult it is to gain clearance under other circumstances.