I've met a few people like the sister's friend, in that they claim the "Syndrome of the Month" until they meet someone who actually has it.
It's sorta like the unpopular kid in grade school who claims to speak German, until he or she finds out that another classmate or teacher meets actually speaks German. The kid will then make every excuse to avoid the real German speaker, so as not to be exposed as a fake. As long as everyone else believes the kid speaks German, he or she gains some popularity; but as soon as he or she is "outted", they're even worse off than they were before.
The sister's friend may be in a similar situation, in that she won't be outted as long as she avoids the OP; who may be fully able to point out where her self-diagnosis may be in error.
Then again, once she learns how a real autistic person behaves, she may start behaving more autistic.
_________________
No love for Hamas, Hezbollah, Iranian Leadership, Islamic Jihad, other Islamic terrorist groups, OR their supporters and sympathizers.