From what I see from Ep1-3 (ignoring Ep4) she's broken and irreparable. Any further relationship or discussion between the two women would have to be real ordeal for Erica. While they have a connection by being psions and having their brothers killed by Cain, this is also a woman who butchered Erica's love interest Sully, murdered her boss and father's friend Davies, and put Erica through mental torture when she had nothing to do with what happened to Cordelia.
I think it's funny to realize that, chronologically, the timespan between visiting crime scene in Ep1 (2 AM) and ending Ep3 is less than 2 game days. I'm surprised Erica hasn't fled the country yet with all she's been through.
Cordelia might not have been a bad person 6 years ago. 6 years ago she was younger, passionate for her family's well-being, and also a little naive. But 6 years is a long time to digest certain things, like shooting your brother point-blank (knowing that it would happen), locking Cain in chains, and knowing that it would take 6 years before anything could be resolved. Could you imagine knowing exactly about something that happens in 2019 and you're just waiting and waiting every day for it to happen so you can finally do something about it? Even knowing that you were going to have a shootout with the woman that day, and knowing where to shoot so that it would always miss her?** It would drive someone insane beyond repair.
In the two days that Erica's known Cordelia 6 years later, we know her as someone who deceives/uses Erica, is directly or indirectly responsible for the deaths/mutilations of her co-workers, and is mentally screwing Erica up. The Cordelia we saw 6 years ago is not the Hat Killer we see now.
Back when I was being introduced to Ep1, I mentioned (before I knew the story) that I thought Rose would be the opposite archetype that she is in the game, and I had originally imagined Rose as a femme fatale living in a seedy apartment. A balance between her life of order (FBI agent) and her life of chaos (learning to be a psion). I thought that Erica would grow to become increasingly insane as she continued to train with Rose and kept using her powers more and more until she broke. A "rose" is a nice thing to look at, but if you toy with it too much, you'll prick your hand on its thorns (in this case, using your powers too much).
But it turns out that in this story, it's Cordelia who goes insane, not Erica (and under different circumstances). "Cordelia" doesn't exist anymore. She's just the Hat Killer now. Broken, but redeemable.
**The dichotomy between this and Ep2 where Cordelia can run Erica over in a car has always bothered me. Maybe Cordelia figured if Erica's stupid enough to stand in front of the car she deserves to die I guess
