Realizing that there are a few months before we get any more story, I think I'm gonna get a little bit of stuff of my chest and then try not to dwell on it anymore, heh.
I think the big problems I have with the MC/Jaye relationship are as follows:
We're told MC loves her, but we're never given a chance to. I have this issue also with games where you start with a wife/girlfriend. You're just told your character loves this person, but you're not given any chance to form an attachment to them before the parade of other options marches in, and you get to experience meeting/forming a relationship vs it just existing.
She's sweet when they're kids, but then MC makes one mistake, and it radically alters their relationship for the rest of the game up to this point. So a vast majority of the Jaye we experience she's being a pain in the ass at best. This makes it very difficult to sympathize with her, or be anything other than annoyed by her antics. (Note: I'm not saying MC is blameless in this, he absolutely isn't, just my view of Jaye is obviously influenced by what we've been shown, because we've only seen it from MCs perspective) This is also not helped when he's telling the story to the bartender, we're only told about the nice side of her (Birthday presents, going to games, washing his uniform), but we're shown the antagonistic nature of their relationship. We're being set up to hate her, but told that we love her, and it doesn't really work for me.
The only time I can think of past the very beginning of the game where she shows she's anything other than an angry, petty person is the texts she sends him after meeting with the lawyer, which is immediately forgotten on their next meeting and she's back to anger and insults.
Basically I feel any relationship with her, platonic or otherwise, is likely to just be exhausting, and with no actual benefit at this point. And I definitely don't feel any love for her.
Also as to her +1, my initial thoughts are, as others have said, if it is Christian, I'm pretty sure just walking away is the only option. No amount of money or anything would be worth having someone so aggressively hateful in your life. I'm guessing/hoping she's bringing someone that will remind MC of Christian, another body spray wearing tough guy douchebag, maybe someone she met at school, to get back at him for Mallory.
Even if the silly theory I have on George manipulating their relationship is true, that likely only started when MC left, and he saw it as an opportunity. This shit was broken way before then.
EDIT: Actually if it is Christian she brought, the only acceptable choices will be after I grab MCs shit, swing by Mallory to give her a heads up that his sister just brought a rapist on board, does he go back to Linda or Fiona?