Okay, the more I'm thinking about this "Maybe she's a Kenobi" thing, the more I'm seeing possibilities for it happening. Not that I think it'll happen (it's probably a lot more narratively simple/cleaner to just have her be Luke's daughter, if only so that the final confrontation is Luke's daughter vs. Leia's son) but...
1) We know that the production had been, at one point, looking for someone to specifically play a Kenobi relation. At the time, that news was attached to casting rumors around Lupita Nyong'o, but considering people also thought she'd be playing a sith or something back then, I think it's possible the Kenobi-relation tidbit was misinterpreted the wrong way and attached to the wrong actress. But that's kind of a leap, I know.
2) That RHYMING POETRY bullshit that we ALL LOVE SOOOOO MUCH in Star Wars could be applied here pretty easily, honestly. If she's a Kenobi Granddaughter somehow/someway (man, wouldn't it be nice if this was some part of a spinoff story about ol' Ben on Tattooine), then you have a scenario wherein Luke takes in Ben's offspring, watches over her, basically adopts her as his own and then has to stash her on a backwater planet while he goes into exile, to keep her safe from the imminent threat that is his failed apprentice. Which would sorta kinda explain
3) his look at the end of the movie, where he seems uncomprehending, unsure, and not entirely happy. More bittersweet than anything. Because he's seen this before. It's looping back in on him. Whether she wanted it or not, his failed apprentice has affected her life, and just like Anakin's saber started him on his journey to becoming a Jedi, here she is, holding the same saber, wordlessly asking him to do the same for her, so she can do the same thing he set out to do all those years ago.
It's like poetry.
It rhymes.