[Arthur] Nadine is a ghost. (with explanations as to who she is)

Based on what we see of Nadine, there is a strong possibility that she is a ghost. The most obvious piece of evidence is who sees her. Adults and older children cannot see her. The only people who can see her besides DW are Kate and Pal. In addition to preschool age children, animals and toddlers are also very susceptible to seeing spirits. So far, these are the only people who can see her. She is also shown to appear and disappear and be able to manipulate time. If she is a ghost the question needs to be asked, Who is she. Here are some explanations

  1. A dead sibling- She could be a sibling that died either before DW was born or while DW was really young. If this is true, it could be that Arthur was somehow responsible for her death. This could be one explanation for the parental favoritism shown frequently throughout the show. There is one main issue with this however, Nadine's last name. She is shown to have a last name that is different from the reads. However, if DW doesn't know she's a dead sibling, she could have made up the last name
  2. A kid who lived in Read's house before they moved in- Whether somebody lived in the Read's house before them is never mentioned but is definitely possible. If this is true, it is likely that Nadine died in some sort of accident. It was probably something a normal preschool child would do. This would explain why she functions mainly as DW's conscience. In One episode, Nadine reminds DW that she is not allowed to cross the street by herself when she threatens to run away. Nadine appears many other times when DW is about to something bad or dangerous.
  3. A kid from DW's school-It's also possible that Nadine could be a kid from DW's school who passed away. With this explanation, she could still be a ghost but could also just have materialized from DW's memory of this kid. If she's not a ghost, they don't necessarily e have to be dead but could have moved away also.
  4. A guardian angel- Nadine could also be another spiritual being such as an angel. This would also go well with her role as DW's conscience.
  5. Another relative- Nadine could be one of the read's other deceased relatives (likely one of the missing grandparents) taking the form of a child in order to protect DW. as to why she appears as a young girl, it's likely to make her more relatable to DW.