Considering how long this conversation is going on I would recommend shifting it to a discussion page if you're planning to argue this any further.
But to sum up:
-Clarith has not been mentioned to be a saint, so it's highly unlikely she's the one that tweet girl is supposedly revered as. Even if she was, she certainly isn't the kind of figure that would be outright worshipped as that implies.
-The girl in the tweet doesn't fit Mariam's stated MO. This is fact. Whether or not Mariam is proficient in, or has ever used, a gun is never clarified. What we do know is that she's very skilled with knives.
-The girl in the tweet doesn't fit with Mariam's backstory as we know it (though it is true there are gaps in it that doesn't rule out that aspect entirely).
-That tweet is in a set of other tweets that references obscure facts that may or may not actually be related to Evillious, including "dead soldiers", "a tiger who isnt' a tiger", and "a 'nothing country' that actually has something in it". None of these sound on the surface like they're related to the Story of Evil specifically.
There are lots of assassins in Evillious, and we hardly know anything whatsoever about the main conflict of Judgment. We also know hardly anything about the Expansion War. However, both of these things are going to be released by the end of the month, so answers will come then. Pretty much all arguments either way rely on assumptions and speculation, and things that could possibly be true.