It comes up from time to time. It's somewhat standard for the vampire genre, though, so the jokes are in every fandom I'd imagine. "Don't play with your food" etc. The one from WWDITS, if I recall, was in a discussion of why they prefer virgin blood and one of the vampires crudely described it as you're enjoy a sandwich more if you knew no one had had sex with it.
With Twilight they are never so straightforward about it, but in the movies Bella does joke about how she might 'become the meal' so it's sort of acknowledged. I think part of it with Twilight is that it is SO sexually repressed (until marriage! whereupon she immediately gets pregnant!) that it doesn't come up in the context of sex so much as just, why are you hanging out with your food, why are you in love with your food, why do you want to marry your food? But even so, the Cullens do try to see humans as people and not just prey so it's more the other vampires seeing it this way (the "you brought a snack?" at the baseball game, for example).
What seems MORE strange to me, personally, is that it's CANON LORE that male vampires CANNOT reproduce with female vampires, but CAN with THEIR FOOD. It's even canon that the MORE DELICIOUS A WOMAN SMELLS TO A SPECIFIC (MALE) VAMPIRE, the higher the chance of conceiving. So not only can they have babies with their food, the chances of Baby are higher the MORE DELICIOUS the food is. Like why . . . why would biology work that way. Why would one half of the species retain fertility while the other didn't? Why can they reproduce with their intended prey? Why does the deliciousness of the specific prey make it easier to conceive?? That makes it a million times more likely the human dies and the pregnancy doesn't proceed. It feels so specifically designed just so Edward and Bella can have a kid; like the entire universe, in-world science and lore bent to their needs.
Edward had sex with the most delicious sandwich ever and had a half-sandwich child with it. What.
