Psychotic means to suffer from psychosis. Having psychosis means there is no sense of reality and suffering from hallucinations.
In real life she is 17 years old, in the show she might be 13 or 14 years old, although it's kind of confusing, because in the epidsode "imake sam girler" it says that there was this one physcothic senior that bullies everyone, so obviously sam is at least in 7th grade. The confusing part is when I watched the brand new icarly epidsode "itwins", when Carly answers her door and sees Sam's twin sister, Carly says that "she hadn't seen her since 7th grade" and by the way she said that, it made it seem like they were in High school. Sorry I don't how old sam is on the show.