Since you didn’t write all the options, we cannot answer for sure.
However, I would say that her work is definitely reliable, since she talked to people who repair cars for a living, so they definitely know what they are talking about. Also, she read a lot of these magazines which thoroughly explain everything she needs to know. And finally, she researched many types of cars, which means she has a wide scope of cars she is familiar with so she can indeed help others.