I tried this today. I had 2 keys from Kickstarter but I only ever redeemed one. Today I redeemed the second one (Steam key) and activated it on my girlfriend's steam account.
Both versions of the game show up in her game library on steam but only the non-enhanced version is installable. The Enhanced Edition just says 'GAME PURCHASED Today' but no install button appears. I tried installing the regular version first to see if that helped and tried logging in and out of Steam. Neither helped resolve the issue.
I've contacted Larian support to see what's up.
