By the order of Royal Scientist Undyne, all of Sunnedout is evacuated, therefore Muffet's is empty.
Muffet will be there as usual, but depending on who you kill, the place will be different.
- Sans: If you kill Sans, Papyrus will not be there which worries Muffet since he was her best customer. Also the customers there wonder where he went.
- Any of the royal guards: If you kill any of the royal guards, they will not appear in Muffet's.
True Pacifist Route
Muffet will praise your "good job" in the True Pacifist Ending Epilogue.
Muffet is either mute or speaks a different language than other monsters. Another monster tends to speak for her which is revealed at the end of the True Pacifist route.