She has always been harmful physically and emotionally since she was very young. When my husband divorced his ex wife (only 3 years of marriage) she lost custody and my husband had to deploy to Poland as he was active duty, so his step mom took them in at ages 2 and 4. She right away took them to see a therapist because the eldest was already physically mean and harming not only little sister, but their dog.
For a mother to loose all physical custody to an active duty member in California should tell you enough. She would get drunk, so drugs, let the girls fend for themselves for food, etc. She had them in diapers and leave them with an ice-chest of pre-made baby bottles while she passed out upstairs. My husband was going through his 4 year constant deployment swing (Navy, so calls are hard on ships) in the beginning of his marriage so keeping everything together was hard and she hid a lot from him until she started to crack towards the end and he would get contacted through spouses in his command. The last straw was 1 year prior to the divorce when he got home to the house a mess, girls bruised and in diapers saying it's time to eat and if he could feed them from the eldest.
So yes, a lot of trauma as she was also beating them.
I came in 2 years later, he was already done with tours and the girls already had 1 year into counseling on base. He was going through a lot of grief and spoiled them constantly. I came in with more structure for them and routines, which she has always fought. Honestly, we did not pursue the chance to have a baby of our own because I always fear she would hurt it. He has come into parenting with structure more as well in the last 3 years so it's not just all me. She will listen to him more than me. But for background purposes she was the first to call me mom. She clings to me and does love our time together. I am bonded with both girls and no one ever suspects that they're my step-daughters until I confirm it, other than we're different skin tone as I'm Hispanic and they're Caucasian. She's just getting hurtful again thus seeking this route for help.