Does anyone remember this book....

Hey folks, longtime lurker, first time caller. Just a little about me: I was always interested in 40K, mostly through video games, but I finally took the plunge when I grabbed the first Eisenhorn book on Audible to pass the time while sitting with my dying father a few years ago. Needless to say, the grimdark has been a great source of comfort during some trying times and I'm now up to almost 80 books in my Audible collection, starting my print collection with my favorite series (the Nightlords omnibus!) and resisting the urge to jump into the hardcover collecting (the heart wants what the wallet does not!).

Anyway, sorry for the preamble. My question for the experts today is related to a book I read about 20 years ago that I'm trying to find the title for (I had borrowed it from a coworker). I really enjoyed it at the time and have been searching for any clues about it since I've started my fulltime reading. It featured a female protagonist (I think she may have been either an Arbites or Inquisitor) coming to a hive world where she gets involved in an investigation into Chaos on the world. At one point, she loses her arm, and in the end, she leaves with the Chaos antagonist, presumably into a sequel.

Does this plot sound familiar to anyone? Did I dream it? Am I still dreaming??? (if anyone has any clues into the title or my waking state, I'd be happy to hear it! Thanks!)