My gf's hair is weak and damage. How to help her recover her hair?

My gf went to hair salon to straightening her hair. The result wasn't great and she was crying for it. She uses "ENJOY Luxurious Shampoo and conditioner" helps to strengthen hair but she doesn't satisfy much. She also uses Healing Oil of Dr. Miracle every night before she goes to sleep. She is wondering are there any tricks to make the hair shine, firm, and smooth? She is not African American so if she tries carrot oil or any oil from African best treatment will that be ok on hair hair?