Frankly, prostitution is one of the most perfect career choices for Selina.
For me, while I've no problem with it being one of the most perfect career choices for her personality-wise, I think she'd go straight for the *most* perfect career for her, which is thief. Theft is also hugely flexible in terms of working envirotnment, huge renumerative possibilities, no bosses, no contracts, you don't ever have to formally resign, you can't be fired and it's totally free and independent. Obviously both careers have different advantages/disadvantages (like any career), but since I know Selina as the greatest cat burglar, I would much rather see her trying out different different types of that career, because I see being a thief as being a huge part of who she is, her natural job, and one she would have naturally started doing very early.
Miller doesn't seem to have any feel for that at all here. She seems like a big bruiser who just later decides to grab things after knocking people out. (Also, I'm not so sure Miller doesn't mean her "never met a man" to be Selina speaking the truth in the guise of the role she's playing for her client, which doesn't make her seem happy in her line of work.)
Also, I just don't see Miller is presenting prostitution as linked to freedom in his world. Iirc, the scene right before this has Bruce announcing he's come to the worst part of town, in a panel that emphasizes the sex work going on. Selina leaps out of the window saying "nobody hurts Holly" referring to Bruce hitting her, but the pimp has been treating Holly like dirt from the beginning. It seems like Holly, at least, *does* have a boss. In these panels, I'm seeing the lives of these women being presented negatively, with Selina "rescuing" Holly by taking her away because she's had it.