You know, apart from what ZUN canon says I always had a bit of doubt about Flan being a vampire. I mean, Remi is obvious enough but Flan always seemed to me to be some sort of greater demon or something rather than a vampire.
ZUN's canon does not necessarily compute with the standard mythology. I actually remember something about Remilia being rather fond of garlic and not giving a damn about crosses or other holy symbols.
Randeel said: She is eating garlic. Vampires and garlic doesn't mix well together.
It's not garlic. It's Rakkyou, a type of leek. Though it still might be mildly toxic to Flan as leeks and onions aren't all that far off from garlic. http://en.wikipedia.org/wiki/Allium_bakeri
I added it into the How is that even possible pool before finding out it's not a garlic. Feel free to remove it from that pool if there's nothing wrong with her eating that...