We are very familiar friends. She suddenly sent me a short message, only my first name, no last name and nothing else. Why?

Love grows with time. When two people are together for a long time, they will gradually develop feelings. Maybe this girl has always had that kind of interest in you, but you didn't realize it. If it is a date, is she the kind of girl you like? You'd better talk to her and see what she means. If you think you can't be friends, tell her well and don't hurt her. The two lovers finally got married.