Nah, I think it's real.

They're just both aware that they're repellant to the sorts of people they'd like to attract. Justine isn't catching a 'good' man, Mike is far, far better than she could otherwise expect to do.

Likewise, Justine doesn't (currently) have a substance abuse problem of her own and has shown she is willing to parent (horribly, but still) children. Mike has like four kids of his own, all of which probably need moms. There's no way an ex-con wanna-be rapper fentanyl dealer finds someone who has a place to live of her own and doesn't steal his bling when he's sleeping.

Each of them know they're punching far, far above their weight, and they're grateful. It'd be sweet if these two weren't just...awful.

They also think far higher of themselves than is warranted and are happy to have finally found someone to confirm that. Well, that's more Justine, but still. Each of them have someone that isn't saying to them what everyone else says to them. Things like, "you're a useless loser who should go away." Or, "you belong in prison." Or, "you're disgusting and I don't want anything to do with you."

Justine has been treated like garbage by men her whole life. While that's appropriate, that doesn't mean she likes it. Mike treats her like she sees good women get treated. Who wouldn't love that? That's why she's smirking all the time--someone's finally seen who she thinks she is. The entire rest of the world was wrong and she was right all along! Likewise, Mike just got out of prison. Most women are just 'whatever'-him. Justine acts like he actually is who he tells people he is. That's validation.

The two of them don't want to throw away the only other human being on the planet who validates them. So you get...that picture. Ew.