Factual error: When asked by the Princeton interviewer what he plans to major in, Joel replies "business." Princeton does not offer an undergraduate degree in business.
Factual error: Tom Cruise smokes a few times in the movie. He has a pack of Marlboro regular which normally have a brown filter, but whenever he pulls a cigarette out of the pack it has a WHITE filter, this leads me to believe it's a Marlboro light coming out of a Marlboro regular package, to protect his film-star lungs.
Answer: Lana liked him, but was not in love with him. The whole Guido house raid was his way of getting what's owed to him, when Joel stole all his business. At the end of the movie, Lana and Joel walked and talked about him going away to college, with no expectations about one another continuing their relationship.