with the fairies

away with the fairies

Seeming eccentric, distracted, or a bit crazy. I can't follow what your mom is talking about—it's like she's away with the fairies all of a sudden.
See also: away, fairy
Farlex Dictionary of Idioms.

(away) with the fairies

giving the impression of being mad, distracted, or in a dreamworld.
See also: fairy
Farlex Partner Idioms Dictionary
See also:
  • away with the fairies
  • be away with the fairies
  • (as) crazy as a peach-orchard boar
  • boar
  • be miles away
  • lose the drift (of something)
  • lose the drift/thread of something
  • (as) mad as a March hare
  • (as) mad as a hatter
  • be out there
References in classic literature
The best proof of this was his caution with the fairies. They were most anxious that he should remain in the Gardens to play to them, and to bring this to pass they tried to trick him into making such a remark as "I wish the grass was not so wet," and some of them danced out of time in the hope that he might cry, "I do wish you would keep time!" Then they would have said that this was his second wish.
The Little White Bird
ALNWICK Garden will be hoping its latest idea is now "away with the fairies" after creating its very own magical fantasy world.
Fairy tales fun in the Garden
Janice Gough is quite literally away with the fairies.
The nurse who gave up her job .. to be a fairy; EXCLUSIVE: MEET THE MUM WHO TURNED HER FANTASY INTO A MONEY-SPINNING BUSINESS