Marla and the Romantic Triangle

The romantic triangle between Marla, the narrator, and Tyler is confusing because although it's a triangle, there's really only two people involved- Marla and the narrator/Tyler. I've seen countless tv shows and movies and read numerous books with love triangles, but never one where two people were really one person, so this was really interesting to see. I think it's the mystery that surrounds the narrator that makes him attractive to Marla. He goes around acting strangely, which is better seen in the movie because you can see Marla talking to the narrator and Tyler like they're the same person (because they are the same person), but they both have completely different reactions to Marla, and this is confusing both to Marla and to anyone who does not yet realize that Tyler and the narrator are the same person. I think Marla still cares about the narrator because she spent so much time being alone and going to support groups alone, and then came the narrator. She finally had a friend that she could cling to, even if they acted like they hated each other.