Mohini was on the terrace of her Hanuman Gali residence watching a neighbour's wedding procession when a youth in an inebriated condition fired in the air, injuring her near the eye, they said.
The girl has been admitted for treatment to the district hospital, they said.
While those responsible for opening fire fled the scene, the bridegroom and his uncle have been taken into custody till the arrest of the accused, police said.