I've replayed it three times, and I still can't trigger Victoria's scene
1) Is Victoria preg BEFORE you start the Waystones Part-2 quest?
2) You picked up Succubus after she went shopping? After the "Retrieve The Tools" quest.
3) Do you have the Spcey Content mod installed (properly) because without it u cant have sex withSuccubus, so you cant have that scene.
4) If you have both those criteria she is horny & it's the evening, then go upstairs & Victoria MAY be there. If she isnt trying going downstairs & back up to see if she spawn in (may need a couple tries).