the basis is that she used to sell her blood to this vampire for money back in the day when she first moved to portland. they had an agreement that this vampire would never actually bite her, and it worked out well for a while. they got their witch's blood and she got to live in a nice home, drive a fancy car, etc. except when she finally wanted out of their deal, things didn't end so nicely for her. i was thinking they moved out of town for a while, but there was always the unspoken implication that they could come back and take her blood if they wanted. i was thinking that was probably the scariest part, not really knowing for sure if/when this vampire would ever come back. but some of that can be switched around if needed!