Who else ASIDE from members of Project Mayhem to whom I already proven were figments of the narrator's imagination did Marla interact with? Those are the same guys that interacted with Tyler TOO. Also, why are you acting like the narrator doesn't play out his actions through Tyler and Tyler interacts with real people too, like with the mob boss for example? So her getting money from the the lady at the thrift store means nothing, especially she never actually SPOKE to the lady.
Not to mention the when the apartment scene, and I stated this out earlier as to why she's not real, because this was the more damning. FIRST AND FOREMOST, how did Tyler (the narrator) knew where she LIVED. She only gave out her number, nothing about her address. 2ND of all, she was counting down to TEN and Tyler was able to get from the house on Paper Street which was stated being miles away from everything to HER apartment in LESS THAN 10 SECONDS FLAT. Who made the phone call for the police of a possible suicide? How'd would anyone ELSE know she took pills that COINCIDENTALLY are the same pills that the narrator was given to by his doctor at the beginning of the movie? How did Marla NOT recognize Tyler if she's a "real" person and therefore would of known whom she was looking at? Because she was just on the phone TALKING to the narrator and if she was "real" then the narrator is who she would of been seeing and NOT Tyler, yet she sees Tyler as if he was a total stranger. Why they BOTH not have reflections from the hallway mirror while leaving the apartment?
Marla doesn't exist. She is the contrast of Tyler. Simple as that.