Nurse Ratched--as the supreme, authoritative, and callous overseer for the mental ward--probably believes that she is crucial to the mental-health recovery of the patients. Whereas the viewer believes Ratched to be the antagonist, she likely views herself as the protagonist and McMurphy as the antagonist.
Ratched views the other patients as abnormal people with many mental problems who need her help, specifically in the form of therapy sessions, to straighten out their lives. She believes that the best way to help angry people--such as Taber--or the shy, unconfident Billy Bibbit is to psychologically control them to get at the root of their problems via therapy sessions. It is clear Nurse Ratched genuinely believes she can be helpful to the patients, but only in a strictly ordered, central-authority-figure-dominated-situation. This is why, when McMurphy, a challenge to her dominant control over the patients, enters the situation, she turns up the battle for control of the patients by taking away their cigarettes and not letting them watch the World Series.
She views McMurphy as a rebellious trouble-maker--as an antagonist--and her goal is not to help him (like her goal is with the other patients), but to beat him at his own game.
The electric shock treatment McMurphy received was certainly advocated by Nurse Ratched. She believed that for most of the patients, therapy and anesthetic medication was treatment enough for her to help them. However, with McMurphy, she constantly baited him, so he would overreact, and then would justify the escalating treatment he received. The shock therapy clearly did not help McMurphy's rebellious personality. When McMurphy attacked her after she psychologically bullied Billy Bibbit, she oversaw his lobotomy. In her point of view, it was necessary as it would make McMurphy into a 'vegetable,' completely eliminating his rebellious, different personality.