I don't know Ambers symptoms, although she mentioned some earlier in the thread.
As for realizing if something is wrong, I don't know Amber's story, but I do know that often a diagnosis of Huntington's comes long before the first symptom ever shows itself. Because it is genetic, if one of your immediate family members (parents/grandparents/uncles, etc) has Huntington's, they will monitor all immediate family members, and sometimes do genetic testing.
That was how my friend got his diagnosis, he doesn't even have any symptoms yet, but has Huntington's disease. His father had it and so all the children were tested. It may be years after a diagnosis before a person shows any sign of Huntington's.
Huntington's is an autosomal dominant gene, meaning in most situations, a child has a 50% chance of having Huntington's if one parent has it.