Despite popular lore and the interesting speculations of a gentleman named Stoker, every vampire Anna has ever met has had a reflection. This means they also show up on film, and in handheld video cameras such as the one carried by our young hero here--but if Anna had her preferences, this is one bit of cobbled together mythology she'd keep.
Showing up in photographs is a poor tactical choice, for one thing; the line about how you had an ancestor who looked just like you gets old after a while, and secondly she just--doesn't like it. This is perfectly normal. Many people are not wild fans of the person they become trapped like moths under glass, and they hold this opinion without being a member of the unliving.
Anna tells herself that it's tactical. It makes her feel better. So when she sees the boy with the camera she's prepared to cut across the other side of the park in avoidance, but something about him is--strange. The way he smells, like coffee and tiredness and misery, and under all of that is blood. Or the way he holds himself, or--just something. Something unfamiliar in a way that feels like she ought to know it, and those things bother her. She doesn't have holes in the perfectly constructed latticeworks that protect her; a lack of knowledge leaves a person unguarded. Even if she's learning just to stay the hell away, it's important to know.
So instead she slips silent and fast as quicksilver out of sight and watches--she's doing a lot of that lately and it feels like life before the comet, when she was a shadow. A wraith. A pale sick little monster with teeth like pickets cut from pearls. She doesn't know whether this is better or not, but--she is very good at watching, still.