"In terrifying nightmares, she relived the accident", this sentence shows that something traumatic has happened to the character, and the fact that she still hears the "screams of the other victims" shows that she is not past the accident. She also deals with persisting pain. So this trauma she is facing is what she needs to overcome.
My last answer was deleted for being pointless, but I had to add more letters for the correct, succinct answer to be published. The right answer is "a sentence".
