If the stuttering is not 'normal' and if she is evidently anxious when confronted then maybe yes. But there are people who get lost easily when confronted, so they stutter even if they didn't do anything really.
Naaaah, Thats a crock of crap. Nerves will most deffinately do that. i do..especially if I am unsure what was asked.
that's one of the telltales. Another is repeating your question before they pause to answer.