It should work, but I may need to double check. However, I never really expected players to want to go from full dom to sub, so it would probably require you to beat her at least 6 times to make her submissiveness high enough to start sub content. (Since the dom/sub variable is one thing, it's probably at +6 at least right now, and has to go to -2 to start a sub date.) You didn't hear this from me, but I might have forgotten to remove the cheat item from the game in the current public update, so if you have that you can use it to adjust Katie's dom/sub variable to get started. If that doesn't work, you could also start a new game and use the dungeon skip option, as that lets you set Katie's dom/sub variable to some degree as well. (You'd just use the new save for the Katie sub content then go back to your normal save in that case.)