Concerns about treatement of an adolescent by attending nurse in emergency department

Good afternoon
I wish to express my concerns about the treatment of an adolescent client of mine who was treated in the ER on December 6. She was brought in for an overdose. She was kept in an observation room on the night of December 6 along with another youth. The patient describes poor treatment by the attending nurse that was both harmful and inappropriate as evident of the patients experience and comments by this attending nurse. The patient does not know her name, however it was midnight. SHe described the nurse as middle aged, white with brownish gray hair. What steps can be taken to address this?