Du’aa’ to relieve worry and distress

Salam,
One of my best friend is having lots of problems in life and due to this she lost her happiness, satisfaction, peace of mind. I am very worried about her. Would you please recommend me any duah so can she be happy again in her life. One more thing I heard of 'Aiyat karema', a kind of vasifa, in this if someone read a specfic duah for 100,000 times then Allah will fullfill someone's problem. Idon't know if this is the authentic way to pray to God. Can you please tell me any duah so I can pray for my friend. I am very worried about her so please reply at your earliest convinence. Please give some advice. Thanks