In this strip minus says that she doesn't think there's an afterlife, to which the man she's talking to says that there "Must be one." After a moment, minus asks him if he wants to go see it. MINUS CREATED THE AFTERLIFE RIGHT THEN AND THERE!
And the fact that she doesn't originally think the afterlife exists, despite having interacted with ghosts before this, is not a Plot Hole. She's answering the man's Exact Words, that she doesn't think that spirits live in a separate plane from humans.
This strip reveals that minus does not have complete control of her powers. (She made her puppy bigger instead of smaller by mistake.) This alone should be cause for concern, as if small and trivial things can go differently from how she intends them, who knows how many more serious problems have arisen from her powers without her knowing it?
We get to see many of those problems throughout the comic, firsthand.
The balloon seller's fate. Being turned into a balloon and popping is actually a pretty gruesome death if you think about it. Also, does it not mean minus basically murdered the guy whose only fault was selling the odd defective product and (justifiably) getting angry when minus popped he rest? Disproportionate Retribution indeed!