If I had to choose other I’d say the other would be Anthea. My reason is because as The MC, Ren, and Aelita explored Zone Zero, they came across the old hospital where the MC was hospitalized in the past. As they ventured through to find the exit Ren and the MC saw documents of Anthea stating she had black hair and 4 children. These 4 being most likely Melia, Erin, Allen and Alice. Why? Because Anthea somehow made her hair blonde as her children’s hair are blonde as well. Another reason for this is when the Blonde quads were together, they formed what we know as the archetype mentioned in Nymiera’s story. So perhaps, Anthea is/was connected to the archetype at one point as well as her kids either before or after they were born. Vitus/Indriad must have noticed this, possibly had domestically abused Anthea (as seen at black steeple castle, hope I spelled that right) and had the 4 children separated. Where Melia(heavily implied Maria Reincarnate) stayed with Anthea and Indriad and Allen, Alice and Erin in the unknown dimension. However, Erin somehow escaped(probably due to Souta saving her). So my best bet, either Angie or the past Anthea whom we carry inside the soul stone may tell us more in v13(hopefully). Anywaaaaay, this is my reason.