Spoilers ahead. Director Rian Johnson might think he answered the question of Rey's parents in Star Wars: The Last Jedi, but he'd be wrong. Despite The Last Jedi declaring that Rey's parents were "nobodies" who abandoned her on Jakku for money, fans are still desperately looking to uncover Rey's parentage, going so far as to speculate on if Rey's mom is in Solo. As with Rogue One before it, fans are struggling to fit Solo: A Star Wars Story into the Star Wars mythology, thus resulting in some pretty animated speculation on Rey's potential mother.
Watching The Last Jedi, it seemed pretty clear that the mystery of Rey's parentage was never really going to be solved, or that even if it did, it wouldn't really matter. She is not a descendant of the Skywalker line or related to Obi-Wan Kenobi. Instead, as Kylo Ren tells her in the film, her parents were ordinary people, junk traders who sold her and never looked back. Though the reveal felt pretty definitive, Johnson has said that Rey's parentage could still play a role in Star Wars going forward, as J.J. Abrams is taking the helm for the third film of the new trilogy, tentatively called Star Wars: Episode IX. "Anything's still open, and I'm not writing the next film," Johnson said in an interview with HuffPost.
The director went on to say that, while he believes Kylo was being sincere, there's always the possibility that he could be wrong (or, lying). "With all of these movies, Obi-Wan's whole speech about a certain point of view always applies, so I think that you have to always think about the context of how information is given," he said. By leaving the door open for Rey's parents to actually be characters in the known Star Wars canon, Johnson inspired fans to look to Solo for possible clues.
If Rey's mom is in Solo, then the most logical candidate is Qi'Ra, the main female lead in the film. As with almost all of the women leading Star Wars, Qi'Ra is white and brunette, which makes her a perfect candidate to be Rey's mother. However, it's unclear how exactly the timing would work out. According to Qi'Ra's official Star Wars bio, she is 18 in the beginning of Solo, which makes her 21 for a majority of the film. Now, Solo is meant to take place about 10 years before A New Hope, and fans will remember that The Force Awakens is meant to take place about 35 years after A New Hope. If Qi'Ra is Rey's mother, then she would have had to give birth to Rey sometime in her mid-40s — not completely impossible, but, given how young mothers tend to be in Star Wars, not entirely likely either. (There's also the fact that Qi'Ra is wrapped up in some pretty dangerous gang activity in Solo that doesn't really lend itself to a long lifespan.)
That said, the idea that Qi'Ra is Rey's mother is very attractive, especially when viewed in the context of the theory that Rey is Han's daughter born out of an affair he had while still with Leia. Cheating with an ex does have Star Wars drama written all over it.
There's also the possibility that it's not Qi'Ra but Enfys Nest in Solo who is related to Rey. It would explain her rebellious spirit and provide an explanation as to why she might have been abandoned (it's difficult to lead a rebellion with a child in tow).
That said, the timeline problems with Qi'Ra remain the same with Enfys Nest. But, who knows? Rey's mother could very well be in Solo. And, if we never definitively find out who Rey's parents are, then they really could be in any movie at any time. We'd never know the difference.