If she indeed has a diagnosis and has been to a special school, she'd need to have been able to fake ASD as a small child. I doubt she had the knowledge to intentionally fake any specific disorder at that time. Of course misdiagnosis is possible or lying about her past is possible if all you have is her word.
Still, none of the things you listed indicate that she can't have ASD.
HacKING wrote:
-They are disagreeable towards other people and sometimes downright demeaning with a tone that sounds intentionally frustrating to hear. They know specific things to say when angry that cause maximum anger from me and others during arguments.
Being disagreeable and having ASD is not a contradiction. Some people with ASD do not have a monotone voice. Both a normal intonation and an intonation that is not appropriate for the situation but not neutral are possible. Not everyone with ASD has too impaired theory of mind to know how to hurt another person with words.
HacKING wrote:
-They sometimes exhibit VERY extreme ASD symptoms such as going nonverbal temporarily and intense stimmimg over sensory overload but sometimes don't react at all to the same stimuli and seem to be "overwhelmed" when they are losing an argument. Inconsistent severity of symptoms with possible agenda.
That you interpret something as the same stimulus does not mean that it is the only stressful stimulus she is exposed to or has been exposed to lately. Shutdown may occur when too much sensory or other stress built up and not due to one individual stimulus.
Perhaps she sometimes fakes her symptoms. However, even if she does, that does not mean she can't have ASD. It'd just means she's a dishonest person.
HacKING wrote:
-They are a pathological liar and admit to making up grand narratives about themselves, their thoughts, and their feelings for attention. Some of their ploys for attention seem beyond the complexity that one with autism could come up with.
Not everyone with autism has the same theory of mind impairments. If she has ASD she needs to have some impairment that affects her ability to do social interaction. An inability to understand how lying works or what lies another person may believe is not required.
However, ASD does not exclude having additional psychological disorders. Whether or not she has ASD, she could have a personality disorder or something else that causes her to be mean and dishonest.