She's a Monster!
Since most of the story is told through Julian's viewpoint, and he is definitely a drama queen, it makes sense that the descriptions are, well, a little hyperbolic. Like, when Carver's mother gets on the bus, she's described as being "[…] encased in a green crepe dress and her feet overflowed in red shoes" (77). Literal description? Probably not. But describing her body in this way makes her seem giant, volatile, and, ultimately, dangerous.
Or this: "[Julian's] eyes narrowed and through the indignation he had generated, he saw his mother across the aisle, purple-faced, shrunken to the dwarf-like proportions of her moral nature, sitting like a mummy beneath the ridiculous banner of her hat" (75).
Julian's vision of his mother is, at the very least, distorted. We doubt very much that her face is purple (red, florid), but we can see that he thinks of her as a literal monster—a mummy. But Julian isn't immune to this monstrous characterization, either: later, "The woman with the protruding teeth was looking at him avidly as if he were a type of monster new to her" (67).