Well she has some pretty big flags for a couple of things, but of course we can only go by what you say and are not psychiatrists or anything...one thing (and I live with this in my house) is a form of attachment disorder. She does not sound like a child on the severe end of reactive attachment disorder from your brief description but you mentioned the neglect and going from place to place and it was likely at that young age her bonding cycle (the baby cries, adult meets needs/interacts, baby learns trust) communication cycle was likely not consistent. And then the illnesses, that too can be a risk factor (if happens between birth and age three) for attachment disorder. The rages can be a part of that, or of other things of course. And the obvious is that she has neurological deficits in the ability to regulate and modulate herself due to prenatal (and maybe postnatal) drug/alcohol exposure. even if she was physically healthy, those kinds of brain injuries can start to happen early in in development and you can imagine, not many kids get off scott free if they have that happen. When you google prenatal drug exposure you will see many of the things you describe. The good thing is if you can get full assessments on her (Occupational Therapist (OT), Speech Language Pathologist (SLP), neuropsychologist) you can begin to learn how she processes the world and there can be many different kinds of therapy that can help.
Thanks for sharing her story, for her situation some amount of play therapy may help but I pray you get a very experienced therapist who knows about attachment and bonding (somewill say but attachment disorder is rare, no it is not....full blown Reactive Attachment Disorder (RAD) may be lower incidence but the attachment disorder area is a continuum and it can go from a lack of trust or being a clingy baby to serious issues).
IT is important to make sure that the therapist works to support your role as being the main person she can trust, not to allow difficult child to triangulate and play off the therapist (they can be sweet to the therapist and then they think, oh she is so sweet, must be a parenting issue, but it is what they had learned for survival when moving around or having other care takers....be sweet and you might finally get your pain relieved or food etc...from random people, but then they go off on the parent, sometimes only in private)...
Take care, I am sure others will chime to comment on your new info. I think it is lovely you are able to care for this child....we get it, hope you find what I have found...this is a very supportive group.