I'd appreciate if we could get back to framing this discussion around Miller's writing, rather than his personal life.
I do think that Miller has difficulty writing female characters, because most of his female characters existences tend to have something to do with sex: they're prostitutes, they want to have sex with Batman, they want to go on a date with Bruce Wayne and talk about in their underwear, etc. And, as you say, because they only exist in relation to Batman.
Mind you I haven't read enough Miller to be able to tell, but would you say the same is true of all his supporting characters in ASBAR? IIRC, with characters like Green Lantern and Superman and Commissioner Gordon, their lives all seem to revolve around Batman as well in ASBAR.