imo there's two ways an author could approach the matter of periods in vampire books:
the vampire hates it, because it isn't pure blood, but it also has mucus, destroyed endometrial tissue, the unfertilized egg and etc. It makes the blood impure - that's why they usually go for the neck, its a less adulterated version.
it's the purest, most delicious nectar they could put their mouths on. bc while it still has a lot of other stuff, it also has stem cells that can turn into another body cells.
















