DEAR HARRIETTE: I’ve been dating this guy for four months. He finally told me he wants to get exclusive, which means introducing me to the most important person in his life: his daughter. This is the first I am hearing of a daughter. He never mentioned her when I met him. It’s a complete surprise, and I don’t know what to do now. She is still young, and having me in her life is huge because I know the type of influence people can have on kids at that age. I just don’t know if I’m ready for that.