Based on my experiences on MUTs, I bet the cyclist DID call out, and the woman miss-understood. That would explain the
"Witnesses said the woman suddenly darted directly into the path of oncoming bikes."

that has happened to me numerous times. I no longer say "on your left" because >75% of the walkers would then move left.
I now just say "good morning (afternoon...)" and that has worked very well for me. Over 95% of the pedestrians either look over their shoulder to see who spoke to them, or move right. Either one is fine.
Terribly sad, but reading it, it really sounds to me like something made her move into the cyclists path and therefore who knows who was at fault and at this point, who cares?