and after all she is giving her 100% to Yash and his family,she accepted them whole heartedly. she is loyal,committed with him. then what is wrong in it if she doesn't want to discuss her past with Yash??? which is very painful,sad,worst than hell.
i don't think she cheated with him. may be many things Yash had which he also couldn't share with Aarti or any one.u never know. so that doesn't mean he cheated with her or others.
cheating which means that which affect ur persent or future life. like Pratik's false promise to Paridhi... but Aarti's past is not cheating with Yash for me at least.