The fact that Annabelle looked at this Nosferatu, who literally disappears at random times because he looks weird and seems to hate interaction of any kind, and said, “I like you. I think you’re my friend now.” And Jasper didn’t get a say. They are just suddenly friends and that’s that.
All Because Annabelle liked that he was nice to her. I think Jasper finds her endearing. Like a cat who tolerates the new puppy. It’s great!