Unstable upbringing

I have started dating someone who is amazing, she has been very open with me with regards to her mental health difficulties she has suffered in her early 20s.

She has a toxic family background and goes through phases of talking and not talking to them. She did not speak to her mum between 14 and 21 and only started talking after her mum caught cancer, she has fallen out with her Dad as he tries to control everything she does, he used to pay her rent and told her who and who she could not come home, what to wear etc, then her sister they used to be close but fell out over her cutting her Dad out. Her Dad controlled her through out her teens.

She has also had a series of various short term abusive relationships where they have controlled her and sexually abused her and likewise she has also had a huge number of hook ups in the past.

She also has fallen out with close friends whom she identifies as toxic and bad for her.

She has regular nightmares about death and abuse and sees a therapist regualry (private)

On the face of it she is hugely successful in career and I only found out when we started dating.

I really want to support her but don;t know how, I come from the typical middle class stable upbringing, most of my friends come from stable families etc. Any advice how I can support her.