Show me the completed quests tab. If you've completed Leslie's section and have the Serpents Tongue then interacting with the door of Sabrina's room should continue the quest
Leslie is the mother right? I don't have a list of missions with her name. I think I know what the problem is. The game version is 0.06.5 but I didn't download it from your page.
get an official version would be my first piece of advice. I can't help you if I don't know where you got it from and if it's an official version or a pirated copy someone messed with or something.
