A check
Your sister says, just stop thinking about it. What is wrong with the advice?
Nothing, it is what the religion asksIt cannot be done. Trying requires you to monitor for the thought, which brings itIt is right, but too hard for most peopleIt works, with enough practice
Yes
You cannot check whether you have stopped thinking about something without thinking about it. That is why the instruction in the tradition is about acting and speaking rather than about the arrival of the thought. She means well, and the advice is unusable.