Mandy Ruskin is a girl who had mental health issues.
She had been in a mental health unit due to her having borderline personality disorder, causing her to experience vicious mood swings. She was committed to the mental health unit after accidentally pushing a fellow Havelock High pupil through a warehouse roof in 2010.
Four years later, after getting into contact with Leo Fitzgerald via Waterloo Road's "Helping Hands Hotline", she comes to the school in Series 10 Episode 9 to meet him in person after escaping from her mental health unit. After she witnesses Leo's brother Justin bullying him, Mandy headbutts Justin in the face and ends up being sent to the Cooler after pretending to be a new student called "Mandy McDonald".
Leo and Mandy later escape the school and run to the Fitzgeralds' house, where they muck around and trash Justin's bedroom. Eventually, Vaughan phones Leo, and after Mandy tries to force Leo to ignore the call and he refuses, she experiences a mood swing and ends up holding him hostage in his own bathroom with a pair of scissors, but Leo manages to comfort and calm her down, and she allows herself to be arrested and taken back to the mental health unit. She is not seen again.