Unlike The Spice Girls, Or Kanna, Chigusa even Shiroi.
In Differing Veins like Resurrection this is not exactly as she planned it.
These three was dead bodies in the past Decade and not just any bodies but the three people who was good friends with her.
As soon as she can she found them dead on separate times, they were considered MIA.
Eris instead of letting them rot away she has teleported them into her Lab inside her Cottage so she could find a way to revive the three.
When she found the time to do it she has placed them in a room where she could study them and Injected them with her blood.
Sometimes after two days she began to hear noise and released them from inside.
Turns out the dead bodies has became complete clones of herself.
What has happened is that her blood got mutated during the Final Rynaxian War by a Mutated form of Tao Mu a Roilyran Remnant of The Roilyran Invaders lead by The Virus Queen.
She entered into Eris' body in attempt to kill her from the inside proven foolish and futile since she has Eliza's Blood and her being the Dark Apprentice.
Her body can absorb her entirely which transformed into a trait that many Roilyrans can do... Mutating Lifeforms.
Which improved her Recovery and Absorbing blood.
But her new ability would definitely put her on the spot if shown off.
So in secret her New Sisters now inhabit the building before they can get the okay to roam the streets.
Due to highly respecting her their was no challenge from them.