Same here, it appears to be a bug based on the fact I progressed through all of the story but Ava and Emma. Now every character says progress the story further.
On a side note there also a interesting path were you can see Luna in the story with those 2 before you see the scene where she creates a form. slightly confusing at first for me.
Sorry for the late reply, but I think I figured it out. I think it's because I'm a workaholic in the game just like real life and never actually went to the house at night, so I didn't get that scene before dating the twins where she appears.
For the Emma thing it might be helpful if her hint was the same as the others pre-second act; i.e. progress the story instead of go on a date. Once you mentioned a second act that's when I realized I was missing actual story instead of being laser focused on figuring out why I can't date her.
