Did you finish A New Pet and Hypnoaddiction quests?
Have you talked to Polkopolka?
I’ve finished Alissa’s quests, hundred percent certain. (I’ve finished every quest to my knowledge, nothing left in the logbook or with the seer). It remains that she is not present on the island or available as an opponent, nor can I invite her to the dungeon.
If you mean whether I’ve finished Polkopola’s Trial, yes. I’ve also been on the date with Nymph. It seems that when I talk with Nymph (or Alissa) there simply isn’t the option to invite them.