At first it would be strangers and enemies , due too her not knowing him. And, ongoing fights out of plain sight where most people wouldn't be at or look (Sometimes at night. 

This is a special case scenario, where the vampire seeks him out from other crowds. Because, of his alien blood origins (Which from her senses)and the strange wrist watch on his arm.

Later on down the line, they become friends, where a certain spark might be grow, if both parties seek the same goal.