1- If he keeps hurting her, you must encourage her to move on. Assure her she will be ok. It takes time but she will be ok.
2- Ask her to read these Duas before she sleeps to stop those nightmares:
Do Wudhu right before you sleep
Be on your right side when you are falling asleep
Read Sura Falaq and Naas before falling asleep
Read this Dua before sleeping:
آمَنْتُ بِاللَّهِ وَ كَفَرْتُ بِالطَّاغُوتِ، اللَّهُمَّ احْفَظْنِي فِي مَنَامِي وَ فِي يَقَظَتِي
Read this Dua as well:
أعوذ بما عاذت به ملائكةُ الله المقربون وأنبياءُ الله المرسلون وعبادُ الله الصالحون من شر رؤياي التي رأيت أن تضرني في ديني ودنياي
Then she blows to her left side 3 times.
3- Ask her to read thos Du’a daily to help her with her situation:
https://www.duas.org/Amn.htm