Mind you, just because he had a tough upbringing it doesn't excuse his actions, nor Rukia's actions in instigating his hero complex for money.
That or she just has craptastically abysmal taste in men while simultaneously being a hoe from whom even children are not safe.
You are clearly missunderstanding a lot of the motivation from what we at leas currently know.
First that scene with their uncle and how uncaring she looked implies the guy had been apparently raping her and for a while already. Wouldnt surprise me if she had been letting the guy 'use' her to compensate for letting her and her brother stay with them, and the guy was possibly blackmailing/forcing himself on her.
And she didnt instigate nothing about the brother, it was completely on him to decide to basically pimp out his sister.
Because the literal next scene is Rukia apparently doing compensated dating when her brother appears to "save" her. So clearly by that point she has been pushed around by her brother and his plans to get money. And reasons there are many; actual necesity of money so they could live and pay their expenses -though it wouldnt surprise me the uncle was still paying for basuc necesities-, that she probably truly wanted to do her best for her brother, and whats mentioned as well, that she probably has a philia that makes her like bad men... Except in this case the bad men doesnt refer to the guys she dates, but her brother pushing her deeper and deeper into that mess.
My point is that she mostly has been only a victim on this, who may or may not had been twisted into enjoying making crime.
But the one time when she trulyhas done shady shit totally on her own without her brother input was when she flirted with the kid, which wouldnt surprise me if it gets explained somehow later as well.