Qi'ra's motivations are got into in more detail in the tie-in novel ('Most Wanted', IIRC?)
You know that character trope where there's the ex-con who's been inside long enough to have done serious time, but not so long as to be institutionalised, and will do ANYTHING (up to and including dying) to make sure they never go back inside again?
Qi'ra is like that, only instead of prison, it's poverty. She has an immense drive to not only avoid poverty, but get absolutely as far from it as possible as if it emits radiation; to make sure there's absolutely no way in the universe that she'll ever be back in that situation. And when I mean poverty I'm not talking about just below the bread line, I'm talking about literally growing up in a sewer. Not just any sewer either, but the absolute *worst* part of the sewer. The part that other sewer dwellers recoil at the mere mention of.
She also has a superficial streak since she equates "nice things" with success and happiness. Even when she lived in the hellhole that was "the silo", she did all she could to make her slum "nice" and to make her clothes "nice". Of course my her standards "nice" is still a shithole and rags, respectively, which she increasingly starts the realise. It all comes from an innocent aspirational place, but it's also driven by a sense of shame that's leading her towards a selfish, consuming world view. It's a drive to not just survive, but thrive.
So yeah, getting closer to Maul makes her job WAY more high stakes, but at least she doesn't have to deal with a violent psychopath prone to mood swings. Maul may be dangerous, but at least he's *sane*. Also, being the second in-line for one of the top 5 cartels in the galaxy means more "nice things" and that little bit further away from the gutter...
I really hope they get Emilia Clarke back in one of the Disney+ shows if Solo 2 isn't in the cards. Qi'ra is easily one of the more interesting characters created for the Disney movies and one that still has a lot of potential for further storytelling.