She is a member of the villainous "True Knot" group, led by the evil Rose The Hat.
Andi is a 15 year old girl, who lures men into movie theaters through online ads, she then robs them and cuts their faces with her signature mark. She, according to Rose, is the first person the group have turned in 40 years.
Andi dies when she is shot to death by Billy just before she can murder a helpless Danny Torrance. But she manages to tell Billy to shoot himself to death just before she fully dies, and is last seen laughing about Billy killing himself, before she finally dies.