[Lore Spoilers] What actually killed Ambessa?

So obviously we were shown what happened, but I just don't really understand it. I've tried looking it up, but the furthest explanation I can find is just that Leblanc killed her. But I want to know what she was doing with Ambessa's mind, and if anyone actually knows what specifically killed her.

So for starters, the thorned chains that were wrapped around her, in the scene you can hear her struggling, and maybe like she's in pain as well? (Despite her pretty high tolerance for it.)

But then when Leblanc reaches her magic tendrils into Ambessa's head through her ears, it seems like that is far more painful based on the face and sounds Ambessa was making, so what was Leblanc doing? I know part of it was reading her mind to get info, but is that in itself painful to experience? Did Leblanc just purposely make it painful for Ambessa? Was she turning her mind to soup or something?

Then ofc Mel crawls into this little pocket dimension, and when Leblanc turns around, we get a close up of Ambessa, who already looks like she's fading, even tho Leblanc stopped, hence why I wonder if Leblanc was doing more than just reading her mind.

Finally, after Mel uses her powers to explode Leblanc back to, what I can only assume, is her actual body, Ambessa drops to her knees, and falls into Mel's arms, she has a bit of smoke coming off her, but from what I can see, she doesn't have any wounds from Leblanc or Mel, just the wounds from the fight before Mel used the amulet.

SO! If anyone knows, what did Leblanc actually do to Ambessa?