Blanca died because of Dahlia and Nicholas Deering... I'm going to work backwards in order to explain myself.
In Anatomy of a Murder it is revealed that Sebastien Dussault killed Louie Becker the tennis pro and Blanca Alvarez the new maid in order to keep his affair with Taylor Stappord a secret. He wouldn't have had to if Olivia hadn't paid Sebastien to seduce Taylor, subsequently making Michael Stappord leave Taylor and getting back together with Olivia.
Now we all know Olivia is crazy, but her insanity isn't the only reason Michael left her. Michael divorced Olivia since she was unable to give him a child and so he turned to Adrian's "disgusting little hobby". He had an affair with Taylor and they married soon after. Olivia wouldn't have paid Sebastien if Michael had never met Taylor.
Some of you may say, "But wouldn't Olivia still pay him to seduce whoever else Michael could have been with?" Yes she would, but Louie and Blanca might not have been murdered.
The whole reason Michael ever met Taylor was because of Adrian's "disgusting little hobby" which also caused Flora Hernandez's death. Philippe Delatour killed Flora and framed Eddie Suarez so authorities wouldn't find out that he raped her. And if Eddie hadn't been framed, then Marisol Suarez would have had no reason to come to Beverly Hills or to meet the other four maids.
In Look Back in Anger it is finally revealed that former friend of the Powells, Nicholas Deering, killed their son Barrett Powell in a car accident. This ties into the Louie-Blanca-Flora-Phillipe equation because of the Powells. For years Adrian blamed Evelyn for their son's death when it was really Nicholas's fault... Or was it?
Nicholas only killed Barrett because on their way to a luncheon, Nicholas was informed by his first wife, Dahlia Deering, that she was having an affair with their maid Opal. The news shocked Nicholas and when he took his eyes off the road he accidentally ran over Barrett. Dahlia's affair with Opal had gone on for a while due to Nicholas always being gone and never caring for Dahlia.
My Point Is...
So unless Nicholas had always been there for his late wife, Dahlia would have never had the affair, Nicholas wouldn't have killed Barrett, Adrian wouldn't have started his hobby, Flora wouldn't have been raped and later killed, Philippe Delatour wouldn't have been killed, Marisol would have never met the maids because of her son being framed, Marisol also wouldn't have met Nicholas and in the process making Opal kill herself, Michael wouldn't have met Taylor, Olivia wouldn't have hired Sebastien to seduce Taylor, Katy may have been killed by the Mexican drug cartel because of the Stappords never adopting her, Blanca would have never met the Stappords as Marisol wasn't around to get her a job and Louie wouldn't have been murdered because Michael and whoever his new wife would be most likely had a child of their own and they'd be a happy family.
SO MANY WOULDN'T HAVES!!!