Beth Chapel replaced McNider when he retired rather than died (or vanished off to the pocket dimension version of Götterdämmerung, I forget which), and became Dr Midnight (using the more common spelling of the word) around the time of Crisis on Infinite Earths in 1985.
Ironically she died before he did, in the Eclipso series, whereas, as you say, McNider made it as far as Zero Hour.
She was also an old girlfriend of Rick "Hourman" Tyler, so I'm sure she'll show up in JSA.