Blackmail and extortion are somewhat slippery crimes you don't see charged much anymore unless you have a Mel Gibson "Ransom" type situation or something akin to it where someone has kidnapped someone else and demands money for their safe return. But it looks like Georgia's statute is pretty broad and a prosecutor who had no fear might charge it. There's criminal libel too, also seldom seen today, but it may not exist in Georgia.
Regardless of the criminal connotations, she is perhaps looking at the prospect of being sued for the tort of civil libel and it will be the pastor, not the State, who will decide whether to file that suit. A letter containing false information delivered to and read by another constitutes publication, a necesssary element of a libel claim.

