Sounds like she checks all of the boxes! I have also looked into some other disorders online. Another popular one on here is BPD since so many HCBM seem to struggle with it as well. And it's genetic. Here are some traits below for Boderline Personality Disorder. I would check this one out too. 

1. Fear of abandonment. People with BPD are often terrified of being abandoned or left alone. SD clings to BM even though she is toxic. She has an insecure attachment to her mother. SD11 is terrified of going out in a public setting without DH. It's not just normal separation anxiety. It's to a point that she freezes and can't function. 

**2. Unstable relationships. People with BPD tend to have relationships that are intense and short-lived. SD11 has the need for constant drama with ALL family members. She is always bickering. You could say the sky is blue and she would say no. SD11 has no real friends. Only "frienmies". She will go days with spending every single second with a friend, only to "we're not talking right now". She has zero stable relationships in her life. 

**3. Unclear or shifting self-image. When you have BPD, your sense of self is typically unstable. SD11 is VERY particular about her "style". Skater clothes, shoes, music she listens to etc. Then she will shift to "I want to shave my head" "My teeth are ugly" "I'm so fat" "I don't look like other kids" 

4. Impulsive, self-destructive behaviors. If you have BPD, you may engage in harmful, sensation-seeking behaviors, especially when you’re upset. SD11 binge eats and is unable to cope with normal stressors. She destroys her own property when she gets frustrated. 

**5. Self-harm. Suicidal behavior and deliberate self-harm is common in people with BPD. SD11 talks about how she wants to die. She told BM and DH that she started cutting. All because DH won't let her pick which middle school she wants to go to. Also manipulative and threatens suicide when she doesn't get her way with her parents. 

**6. Extreme emotional swings. Unstable emotions and moods are common with BPD. One second SD11 is claiming it's the "best day ever" and is so happy. The next couple of days, she goes on a hunger strike and says she wants to die. DH and I didn't see any big events to "trigger" these mood swings. They just happen. 

7. Chronic feelings of emptiness. People with BPD often talk about feeling empty, as if there’s a hole or a void inside them. SD often refers to herself as a nobody. That she doesn't have any hobbies or talents. That she is dumb and can't do things. 

8. Explosive anger. If you have BPD, you may struggle with intense anger and a short temper. SD11 frequently engages in shouting matches. She verbally gets frustrated with herself. "Why am I like this?" "I hate myself" 

**9. Feeling suspicious or out of touch with reality. People with BPD often struggle with paranoia or suspicious thoughts about others’ motives. SD constantly feels that others "are out to get her". She says people "look at her weird." And she thinks "people talk about her." She has the "it's the world vs. me" mentality. And is of course always the victim or target in any situation. 

I starred the traits I see the MOST of in SD11. BM has admitted to openly having this disorder. Doctors will not diagnosis it this young. But I personally feel that she has this alongside one of her already FOUR diagnosed disorders (ADD, depression, anxiety, and ODD). Which makes me think some of them may be a misdiagnosis and symptoms of BPD instead. 

A grandiose sense of self-importance   YES - e.g. future Dr. Bratty McBratFace will cure endometriosis someday.  Once she passes Physics 101 that is.  Also Bratty describes herself as the most 'overly considerate' person there is when she can't show up anywhere on time to save her life.

Preoccupation with fantasies of unlimited success, power, brilliance, beauty, or ideal love YES - see above.  Dr. McBratFace will save the world and end up rich and be able to afford all the vegan food she wants.

Belief that he or she is “special” and unique and can only be understood by or should associate with, other special or high-status people or institutions YES - Bratty can only be understood by other trans non-binary people.  Cis-gendered middle-aged simpletons like myself are unable to ascend to her level.

Requires excessive admiration  YES - Bratty takes about 5 million selfies for any FB post.  Then obsessives over which one showcases her at the best angle.

Has a sense of entitlement ROFL YES - telling SO she was entitled to a room in the 'familial home' when we kicked her out; or asking my friend who she met exactly twice if she can stay in my friend's mother's (who had end-stage dementia) Mexican village for her vacation.

Is interpersonally exploitative – Hahaha YES - After telling Bratty I dislike her during family therapy, Bratty texts a few months later as if nothing happened fishing around for free Disneyland tickets.

Lacks empathy  YES - Bratty told me during family therapy that my experiences were not important to her since she is special, trans, etc etc etc.

Envies others or believes others are envious of him or her  YES - she envies any friend or peer who is 'more successful' than her. 

Shows arrogant, haughty behaviors and attitudes  YES - also immature behaviors - e.g. my gifts are not good enough, my thanksgiving dinner is not good enough (where is the vegan food) etc etc etc

Honestly, many of these things are not unique to teens.. I try to leave the psychological diagnosis to the professionals lol.  If her parents see signs.. they should have her tested.

I do also know that sometimes people different for different people... I was really surprised to see OSD with her friends.. she was a very different person (another reason why we tried to always have a friend with her when we went on vacation.. the ones we took without one were more problematic).

i think sometimes the situation and toxic history can make people "crazy acting".. when they may be generally reasonable people otehrwise.