The only other pre-requisite is to have seen that kitchen scene once before (just speaking with Alexis in the kitchen at 8am will fulfill this role, which it seems you've already done).
It unlocked after the Nicole outing in the basement event. The dialogue before was always about the meeting with the dad.
There is a possibility, because it happens the same time as living room events with Nicole, and I'm kind of fixated with her, that I never played through Alexis's scene completely, as there are A LOT of variations with Nicole in the living room and they are all awesome.
I did lots of quick saves there to see if the event would trigger and may have just always gone back to the Mum. How embarrassing.
Gotta say SAZ, this is by far the best mod I have ever seen.
I tried to play this game years ago, but it had lots of bugs. There were continuity and timing issues all over the place which constantly broke immersion, not to mention unavoidable NTR. You patched together the best parts and made it a truly amazing game. The bonus scene with Nicole in the shower is one of the hottest I have seen in any AVN. Add some sexy sounds and it would have been perfect.
I hate NTR with a burning bloody passion, but dark path/revenge was pretty impressive, and strangely satisfying, thanks to the mod and WT.
Cerberus thanks you for all your hard work.
Even unfinished, the game is one of the best incest/corruption games out there. Hope to see it brought to completion someday.