Ariadne was the daughter of King Minos of Crete. She fell in love with Theseus, and it was she who helped him slay the Minotaur by providing him with a sword and a ball of thread to find his way out of the Labyrinth.
She eloped with Theseus, and sailed for Athens with him. They stopped on the island of Naxos where, for reasons that are not entirely clear, Theseus abandoned her, sailing away while she slept. Some versions of the story suggest Dionysus (Bacchus), god of wine, appeared to Theseus and told him that he wanted Ariadne for himself.
Whatever the reason, Ariadne awoke to find herself deserted by her beloved, hence the "poor demented" descriptor. Dionysus promptly arrived to claim her, although not before she could curse Theseus, causing him tragically to forget to change the colour of his sail... but that's another story.