True, from the grand scale of what's happening with the dark/black moon stuff, I get that Ella as a doll might seem almost mundane in comparison. But the gang doesn't know about all that. No one inside the S.I.N base is aware of what's happening in the real world. Okay, let's say they accept this doll that resembles Ella after they arrive at the monster world, but wouldn't they at least want to ask something about her appearance?
They even have this "bonding moment" at the campfire, yet no one seems to care about the Ella doll hanging around or even ask how this doll is here or what connection it has to the real Ella. From a narrative standpoint, it doesn't make any sense. Even Michael asked MC something like "Do you trust this doll?" come on man, Ella is the one who gave you pills, you know what she looks like, heck, everyone knows what Ella looks like. MC even brought her to the beach vacation party, so at least everyone from that arc knows who Ella is, her appearance at least. Are they really not going to ask anything about that?