>>52137160Lana (Suiren) is based in lilia-lana-i-ka-wai (Hawaiian for water lily) and in japanese Water lily and Siren
Harper & Sarah (Ho and Sui) are based in Hosui (Water spray) and in English it is a reference to Harp Seals (H&S)
So their mother probably has a name referring to water or some animal or mythology sea creature.
Maybe Amabie, Ningyo, Jinja hime, Akugyo, Umibozu
For her western name, I think Nama (from Namaka, Hawaiian goddess of the sea) would be a good choice.