Cisco's all about protecting Darlene from the Dark Army. From what he tells them she sounds like low level F Society, so pretty much just a liaison to Mr. Robot. The assassins were trying to kill Cisco, remember? Dom's FBI superior put out his face, making him an intolerable liability for the Army. WR, Tyrell et al. might prefer to kill Darlene too as a loose end but as Elliot's sister she'll likely need to be kept around till they're done with him. Hence is probably not dead.

WR knows who Angela's parents are, her employment history, her financial records etc. (via Cisco's hack), he just also assumes she's Elliot's hacking partner, thus has a hacker's psychological issues. Or assumes that someone inside her does. He assumes wrong, and she picks up on it - while more or less just a normal, she has a normal's emotional intelligence. WR's lack of empathy becomes another kind of gullibility.