The Exorcism of Molly Hartley (2015) online

Molly Hartley is all grown up, but the unholy demon inside her lives on. Six years after graduating high school - and discovering that a secret pact assigned her soul to the devil - Molly is suspected of murder and confined to a mental hospital, where she wreaks supernatural havoc on the staff and patients. Her only hope is an exorcism by a defrocked priest looking to redeem himself and save Molly's life before her hideous "transformation" is complete...but Satan has other plans!