See, Batman cares more about his mission than he does Talia. But Talia cares less about her mission than she does about Batman. Therefore she is a less independent character than Batman. That's the sexist bit.
It puts her on a level lower than the level Batman operates on. If she doesn't believe strongly enough in what she's doing to continue doing it regardless of whether Batman is with her, out of the way, or actively trying to thwart her, why is
she doing it?
This is not really desirable, either from a purely feminist point of view, or from a larger narrative point of view--it raises questions of how she manages to motivate her army, it makes her nominal goals seem facile, and finally it makes her defeatable at any point Bruce deploys his Bat-mite.
And that's not right. Ra's al Ghul had a more metaphorical hard-on for Batman, too, but he was different from all of the other rogues in the gallery, because he was global. Yeah, the Joker hangs out with Lex Luthor and has been in space, but that's not that characters niche, whereas that sort of thing is right up Ra's' alley. He could be used in a JLA story in a way in which Joker or Killer Croc could not, as a principal antagonist, not just some guy there to piss Batman off. And Talia ought to be pretty much the same.
I suppose the bit in Batman and Son can be read as a "together we can rule the galaxy, but if not, screw you" moment instead, but that's not the impression I got. Like I said, Batman already has the Joker; he doesn't need another stalker.