Its been so long I have no idea how to continue this story.
To do the new content:
- Go to sleep (I also went to Sarah's room and woke her up for some fun, but I don't think that's required)
- She should send you a text message asking you to go to the mall
- Go to her door in the afternoon (or evening I forget) to prepare for the date
- You can now do the date at the mall as a weekend event, and from here it's pretty self-explanatory
I'm disappointed at the illusion of choice the game gives you. Lily texts you nudes and Sarah gets mad no matter what you do; not giving her your phone number at the ice cream shop doesn't actually change anything.