There's really no need for Aqua to have more than a passing acquaintance with Vena. It's not important that they become more than passing figures in each others' lives. Unless either Aqua or Vena want more than that (which Su-jin would strongly object to, but facilitate regardless).

"This party is primarily for inhuman people. There are shapeshifters and vampires and what humans call mythological creatures all in attendance here. The only humans were carefully selected."