It’s not a question of there being “evidence” for her as a shallow character, but it’s just what I, and arguably some others, think. It’s a discussion, and the whole purpose of it is to discuss our opinions. My opinion, as stated above, is that none of what she does is interesting, and she’s ultimately a Mary Sue. Reporting my reply on the grounds of it being the opposite to yours is not appropriate.
Now, it’s time to return to the original topic of this post: who’s everyone’s favourite newcomer in Red Dead Redemption 2?