What do you think Vic sees at the end of Gaiman's "How to Talk to Girls at Parties" that upsets him so much?

Throughout the story "How to Talk to Girls at Parties," there's a hint that the women at the party are not exactly women—or even human. This idea is foreshadowed early in the story and then the narrator, Enn, explains his run-in with these non-human "women" at the party. This is why we can guess as to what Vic means when he says, "She wasn't a—"

In the story, Enn explains his trouble talking to girls....

Throughout the story "How to Talk to Girls at Parties," there's a hint that the women at the party are not exactly women—or even human. This idea is foreshadowed early in the story and then the narrator, Enn, explains his run-in with these non-human "women" at the party. This is why we can guess as to what Vic means when he says, "She wasn't a—"

In the story, Enn explains his trouble talking to girls. He says that while Vic could get away with not actually talking to girls because he's good looking, Enn "did not know what to say to girls." The entire story is Enn trying to talk to girls. The first girl he speaks to is named "Wain Wain" and oddly says after a long speech, "Soon I must return to Wain, and tell her all I have seen. All my impressions of the place of yours." The next girl he speaks to calls herself a tourist and says that on her last tour she "went to sun, and we swam in sunfire pools with the whales." Finally, the last girl Enn speaks to at the party is named Triolet and she calls herself a poem. She says about her people,

There are places that we are welcomed. . . and places where we are regarded as a noxious weed, or as a disease, something immediately to be quarantined and elimated. But where does contagion end and art begin?

After Triolet recites a poem in Enn's ear, Vic comes into the kitchen in a panic and says they need to leave. When they leave, Enn looks back and sees Stella, who is staring at them. Enn's description of Stella is interesting and explains these non-women:

Her clothes were in disarray, and there was makeup smudged across her face, and her eye—

You wouldn't want to make a universe angry. I bet an angry universe would look at you with eyes like that.

All of these clues lead to only one conclusion: Stella, who Vic was with upstairs, was not human. This frightens him so much that he ends up "sobbing in the street, as unselfconsciously and heartbreakingly as a little boy."