Hi! I am living the dream as my gf has been hooked on wh40k books, finishing Eisenhorn and now going through the first Gaunt omnibus. We get to have long conversations about the lore and she is beginning to get interested in the games as well. My own history is that I have two ancient 3rd Ed. armies, generic SM and IG. I played 40k way back, but never competitively. Lorewise I am on book 20 of the HH series, as well as having read Eisenhorn, Ravenor, Gaunt omnibuses. Now I need your help.

Which game would be the easiest introduction for her as a first timer and me with my existing (mostly unpainted) armies? She would like to play an inquisitor or a small squad like in Gaunt, so the rules could be pretty detailed and the game should be fun without needing to throw hundreds into a starting army. Kill Team/Combat Patrol/Necromunda/Inquisitor(RPG)/Something else? Could you also mention how it would then be expandable if she were to go fully down the rabbit hole?