Answer: Obsessive-compulsive disorder
Explanation: This mental disorder, which is characterised by unwanted repetitive thoughts and in order to get rid of those thoughts, those suffering from this mental disorder resort to obsessive-compulsive actions, that is, actions that are repeated numerous times. As a result of this disorder, Margaret has thoughts that are obsessive and possessing her do not give her peace of mind until she has checked everything countless times, triggered exactly by that obsession. Also, due to this disorder, if one of the common steps is missed during the obsessive repetition of actions, there is a panic fear, that is, anxiety that results from not solving the obsessive thoughts.