If Calamity Janet has a Barrel, can she use it to generate a Missed! and then use her special ability to turn the Missed! into a Bang! in order to avoid Indians?
In order to counter Indians, you must discard a Bang! card.
Calamity Janet can use Missed! cards as Bang! cards.
Barrel, however, does not give you a Missed! card when it works successfully - it just causes a Missed! effect that can be used to cancel a Bang!.
Since you don't have a Missed! card to discard, Calamity Janet can't use Barrel to avoid Indians in this way.