Set in a place that idolizes some woman who symbolizes good that makes tattoos appear on other's bodies (thought to be messages from her).
Protagonist is a teen girl who was forced to draw the tattoos and ends up running away and joining a circus with her friend. At the circus, the love interest is the son of the owner (she has red hair and is bipolar), who plays death in the shows and looks like a crow during the circus.
Then the force of "good" turns out to be bad (she just jumps inside a random person when she wants to do/say something herself or influence everything. When she jumps out they always go crazy and die), finds the girls who ran away, she forces them to give the people around them tattoos (which is bad because it's just her way to control everyone).
They end up performing as a duo act in the circus where they use their tattoo powers to communicate and make it seem like the character who plays the symbol of good is controlling the character who's the symbol of evil with her mind. Then they end up having to go back to the school they were from and do a show, and the "deity" posses one of the girls, who kills herself to kill it.
Sorry if this was too long/confusing, I was just listing everything I remembered about it.
Edit: I figured out what it's called!! It's "Ink in the Blood" by Kim Smejkal :)