"She had never lost."
Translation:Elle n'avait jamais perdu.
Ok, the word "perdu" very accurately translates to the word "lost" in English.
So, there are (at least) 2 different ways to use the word "lost" in English, and they translate 2 different ways in French:
1) "I have lost" = J'ai perdu
2) "I had lost" = "J'avais perdu
The first suggests that at a point in time in the past, I lost at something. The second suggests that at a point in time in the past, I had ALREADY lost even earlier than that. It is more easily seen in context:
"I AM out of the tournament, because I have lost" as contrasted to "I WAS out of the tournament, because I had lost"
The first sentence is saying that your current actions are affected by the past (I AM...) whereas the second sentence is saying how your past state (I WAS...) was changed by something that happened even earlier than whatever I am talking about.
That is why the first is sometimes called the "Present perfect" and the second is called the "Past perfect"
I really hope I didn't confuse you too much... it'll hopefully make more sense as you go