I think it being Jaycentric fits your stated goal.
Now that you mention it, I did sort of feel like Alexa was rather two-dimensional, unheard, or perhaps not as fleshed out as we -might- normally like. However, you have explained well why that is right for what you mean to do.
Her sub storyline goes something like this...
(I do this as a kind of exercise to try to wrap my brain around the story, maybe get a better view of it. I might be being too selective or leaving too much out. But here goes.)
Alexa. She's smart and clever. A little combative, almost condescending, but just enough for us to find that alluring. After a little friendly jousting, the chemistry seems to click well enough, so we go to bed with her that night.
She's slightly, but understandably, bitchy with Jay when he gets too pushy about a book that he really wants her to read.
Their friends, annoyingly so, I would say, express their annoyance at Jay and Alexa's courtship behavior.
Ah, but, I always need to remind myself that the lives of fictional characters cannot be easy going like I like real life to be, because drama requires conflict, otherwise nothing much happens. So films require conflict. Each scene requires conflict, they say, or a change of some sort.
Her friend, Fran, expresses her dissatisfaction with Alexa's and Jay's relationship. Fran says that she's not happy with the change in Alexa's personality since being involved with Jay. She says that Alexa comprises too much for the relationship, while Jay doesn't compromise enough, or at all. In response, Alexa merely states that she's in love with Jay. It's unclear, but the implication may be that she agrees, but is okay with that because she loves him.
She seems to have a healthy sex life with Jay, with no indication that she is dissatisfied on that front.
Alexa appears to become more and more insular, less social. She'd rather just stay in with Jay rather than go out.
She breaks it off with Jay.
She becomes jealous and makes an ugly scene when she finds Jay is already dating another woman.
She makes a pass at a Red Cross volunteer.
I appreciate that you often include a non-negative, human portrayal of queer folk in your stories. You're like Kevin Smith that way. But here's where I'll confess that I'm not so sure about the inclusion of this scene. I'm not sure why. I think that why it might feel a bit wobbly is that it is not Jaycentric. That is to say, if we embrace the Jaycentricness of the screenplay up until this point, it sort of comes out of left field. Then again, within that context of Jaycentricness, it might be a brilliant stroke, as this may be the post-Jay-and-Alexa-world; something fundamental has changed. Maybe the world is no longer Jaycentric?
She goes to see the performance of Jay's play. She seems possibly interested in or open to restarting a relationship with Jay.
Okay, just perusing the scene again, the scene in which Casper lambasts Jay for being one in a "weird amorphous coupling," which, by the way, I thought was ugly and unreasonable of Casper, has me seeing that in a new light. At first I was thinking, what if you added that to one of Jay and Alexa's scenes, and had Jay, though more gently so, prodding Alexa with those sorts of...observations. But no. I think I see now how it may be Casper who is doing the heavy lifting for the story. Maybe Casper is in fact spelling out for us why Alexa leaves Jay. Strangely, maybe Casper is speaking for Alexa? Yeah.
I was also reminded of one example in a film,
Synecdoche, New York, in which a poor husband (Philip Seymour Hoffman) is abruptly, it seems, dumped by his wife (Catherine Keener). I only watched it the one time, and the fact is that I "couldn't" finish watching it. But the breakup blindsides him, if I remember correctly. So wanting to portray this kind of ambiguous end to a relationship is not unprecedented, and I'm sure quite natural.
One thing about the story that sticks in my craw is this, which is certainly not to knock it; I'm simply describing an emotional and intellectual response. The friends, Fran and Casper, are almost, or perhaps actually, villains. In a sense, Jay and Alexa are their own enemies, as well.
Young people have their friends. Eventually, they meet someone of the opposite (usually) sex, that interests them. They begin to court. During this courtship behavior, it is perfectly natural for and should be expected that their friends and others become peripheral. If the courtship is successful, they copulate, reproduce, and then spend most of their time rearing their offspring. Our primate ancestors have been doing this for eons. Well, maybe not for eons, but at least since reproducing pairs have taken on the nurturing of their young for extended periods, as humans do. Of course, not so long ago, people lived in extended families, and the care of the young didn't rest -often times, nowadays- almost exclusively on the pair.
Understandably, all of these young people, Alexa, Jay, Casper, and Fran, are the products of the twenty-first century. They quite possibly have no intention of following the patterns that their biology and their genes drive them to follow. That's as valid as the alternative. But they
are bucking up against the natural behavior of human beings, despite what Fran and Casper seem to assume to the contrary.
This does annoy me about their friends.
So, none of this is important to your story, and properly so, I'm sure. But I might still ask, do you mean to say anything about this? Or should it be obvious to me? Are your characters conscious of these things? Is it implicit that young people today (and probably yesterday, as well), expect to find relationships without personal compromise, without having to sacrifice time spent with their other, nonromantic friendships, and therefore extraneous to your story?
Hehheh, just in case, this is certainly not meant to be interrogative. Or maybe it is. I just got into thinking about it. I do not mean to try to cloud things, or to distract you from what
is important to the story.