No it sounds like you did meet her on friday "night" as intended. You go to sleep on friday and then wake up on saturday "morning" at 3AM. so even though you sleep on a friday, you technically wake up for the bonfire on a saturday since its 3 in the morning, if that makes sense.
So, if i'm understanding the issue you're facing: (correct me if i'm wrong) You sleep until 3am, meet lilith, come back to the apartment, player automatically goes back to bed, get text from Ethan in the morning and then the "bonfire quest completed" message. it's now saturday at 8:30, correct? and if you try to sleep, the player sleeps until 3am again as if the bonfire quest is still active? Can you tell me what time and day the phone displays right before you try to sleep when this bug occurs? I am almost certain this issue occurs based on the specific time the player tries to sleep on this day so thats why I need to know exactly what time the phone shows before attempting to sleep when this bug occurs.
And yeah like I said just double check you've completed the homework by making sure the option to do the homework no longer shows up at the computer. As far as I can tell there should be no conflict with the book quest but it's possible i've overlooked something.
EDIT: I believe I may have found the issue. It seems this issue can occur if, on thursday, the player stays awake past midnight (to which it then becomes the early morning of friday) before manually going to sleep. Does this sound like what you did?
The triggering of the player sleeping until 3am occurs when they go to sleep on friday but I overlooked the fact that this could also mean it could trigger if the player stays awake past midnight on thursday before going to sleep (since at that point, the day would be friday), meaning the player would be triggering the bonfire event 1 day earlier than intended. This is an easy fix. I can release a patch later today.