Yeah um, that's all Bruce is, really.
That and he was a thrillseeker and loved fast cars and gadgets (likely even without Batman in the picture), and she looked down on that too.
And Rachel lectured him, constantly disapproving what he was doing instead of letting him be what he was. I'm sorry, but that's not a healthy relationship. Yes, your partner should call you out on your BS if warranted, but they shouldn't want you to be a different person
Selina implored with him to see her side, but she was finally of the "if you can't beat them, join them" mindset in the end.
And now that they're together, I think she'll use her own abilities to make sure Bruce doesn't get too far into the deep end. Alfred couldn't physically make sure Bruce is safe, but Selina can. And Bruce won't make her be someone else, but he can certainly use his charm to convince her.
That's why I felt she was a far better match for Bruce than Rachel was. Incidentally, my relationship with my husband is more akin to Selina and Bruce's despite the fact that we are far more boring.