If Calamity Janet has a Barrel, can she use it 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.