In this case, unfortunately an usual one among humans, lateness can be consider rude or simply an incovenient. Under Shari’s point of view it can be consider rude because Ali was the one who invited her so Shari took the bother to arrive on time to make a good impression to her friend. Also, being on time is polite so Ali’s lateness is unpolite, out of place. Ali didn’t even take the time to let her know she was going to be late, so Shari could have thought that Ali had stood her up. On the other hand, Ali could likely thought her lateness as simple as an spontanous problem, nothing to worry about, and she might not consider it as a big deal. Problably she felt that the meeting with her proffesor was more important that Shari’s dinner so in order to that, she priorized it and did not main about let her know.