For the people who are still unsure about using she/her pronouns for Jax, some things to consider;
Fictional character.
I see a lot of people insisting on following real life etiquette when it comes to using pronouns for fictional characters. This is, almost always, in retaliation to either a trans reading or a trans headcanon for a character. Saying that "But in canon, they only use !"
The thing is, Jax isn't real and will not be hurt by this supposed "misgendering". Besides, if we know that the intention was for her to be transfem, then it only feels right to refer to that, and would actually be… well, gendering her correctly!
This, of course, is not the way to go with real-life trans people, since irl, it's about respecting the individual's wishes. But since Jax isn't real, it really just is a case of "call it how you see it".
In fact, I'd go so far as to say that acknowledging that she's transfem, but refusing to use feminine pronouns because it's "not what's used in canon" comes across as a bit backwards, and makes you look more disrespectful in the process.
Acceptance and visibility.
By referring to Jax with she/her, it shows that you are aware of her being textually transgender. It not only helps spread this reading (because god knows how many people didn't catch on or flat out refuse to see it that way), but it could also potentially help other similarly closeted people realize that they, too, can just… be trans! And that you do not need to pass perfectly to be gendered correctly.
Degendering.
I've also seen people use they/them because they feel as if it's more respectful, since it's still "ambiguous".
To that I say... it really, really isn't in this case. When we have such a clear cut case of transfemininity, using they/them instead of she/her is just plain and simple degendering; Stripping someone of their gender identity because you want to avoid the elephant in the room, or to please both sides of the argument, effectively failing the transgender individual that it's about in the process.
It's a level of disrespect that's subtle, but hurtful. Trans people are held up to a much higher level of scrutiny than cis people when it comes to gender performance, and degendering is one of the many ways in which this manifests.
Outsider looking in.
Since Caine only had access to their social media profiles… who's to say that she isn't already using she/her in private? She's frequenting an alternative bar owned by a nonbinary person, and as seen in the final busstop scene, growing her hair out. And whilst not overtly feminine, her clothes are pretty neutral (and not to mention... a classic dysphoric look).
The journey before the end.
The thing with being trans is, there is always a "before". Before you realize, before you accept, before you come out. Jax's story starts before she has fully grasped and embraced her own identity. It's something that isn't shown very often in media, but can be a big part of someone's trans journey.
I just hope that, one day, posts like this don't need to be made. That by having more characters show the journey rather than just the end result, people will come to recognize and understand trans characters (and by extension, trans people!) innately, and that the bridge between trans and cis will seem insignificant by then.