In addition to dispensing the doses of medication to patients, she is responsible to ensure that patients take their medication rather than keeping it so they can sell it on the prison's black market. However, many patients who receive narcotics are required to pass part of their daily dose to one of the gangs that run the prison. As such, prisoners have to come up with schemes to fool her.
When House receives his medication, he "cheeks" one of the pills so that Nurse Hostetter can't see it when she checks his mouth. However, he knows the pill will dissolve if he cheeks it too long, so he usually has to distract her in order to move the pill from his cheek and give it to the gang leader. In the episode, House points out that she has given the wrong dose to one of the patients, and he takes the pill out when she turns her back to correct the error.
Mendelson is in the habit of making crude sexual remarks to Nurse Hostetter.