Who's the Victim?

I finally figured out why I'm having such a hard time with the fourth Sasha Jackson Mystery. 

Seems that until just now, I'd forgotten about a very good piece of mystery writing advice:  Know Your Victim

When I first began writing, I remember being told to start with the victim.  The author must know who died - of course - but knowing who the victim was, what his life was like, what his influences were, what his values were and so on makes the story unfold for the author (and ultimately for the reader as well).

It's easy to forget this advice since the victim will most likely not be an "active" part of the story.  You won't likely give the victim much dialogue.  There aren't likely to be many descriptions of him going about his day, going to work, interacting with others.  (Keep in mind that in North American mysteries the dead body usually turns up within the first few pages).

In Frisky Business, book four of the Sasha series, I have two victims, both female.  Right from the get-go, I've had a solid background of Victim #1.  Because of this, it's pretty easy to figure out (and write) who killed her and why.  I have a good understanding of what made her tick.  Knowing her well tells me who will be in her life, with whom she would have interacted, and so on; thus I have a pool of characters that my sleuth can turn to during the investigation. 

But Victim #2 is another story... I keep getting stuck on this one.  Everything I've written ends up being deleted a couple of days later.  It finally occurs to me that I need to figure out more of her background.  My gut tells me that once I do that, the rest will fall into place.  
When I know who the victim is, I'll know what else I need in order to write the story.