Does my sister have a post-traumatic stress disorder type of dual diagnosis?

How do I know if someone has PTSD? I noticed a lot of changes in my little sister Ginny ever since our house burned down last year. It was a horrible experience. We almost died from that fire. We lost our house and almost all of our belongings. Our pet dog Snoopy even died during that incident. Ginny was the last one to get out of the house during the fire because her room is situated on the second floor. Our neighbor, Mr. Wilson, was the one who rescued her from the fire. Mr. Wilson died after saving Ginny. My sister blamed herself for Mr. Wilson's death. She told me about having recurring dreams about the accident. She now has difficulty in sleeping and having fun. She also developed a dislike towards everything related to fire: flames, stoves, candles, campfires, etc. Does she have PTSD?

: http://alcoholdrugstreatment.info/does-my-sister-have-a-post-traumatic-stress-disorder-type-of-dual-diagnosis