My (removed) is struggling from a lot of Shak in every issue of her life, be it salaat, wudhu, taharat, etc

Is there any zikr she can recite to help her through this kaseer ush shak

She should know that Imam Sadiq says it's shaytan who distracts a momin from doing good deeds by dragging him/her to shakk and doubts. She just must not pay attention to her shakk and recite la ilaha illulha, salwat and qulhuwallah as much as she can.