The Importance of Ava's Intelligence

I feel like by definition, it's very hard to be aware of what your own weaknesses are. I just kind of assume that it would be essentially impossible to not be tricked by a sufficiently advanced AI. This whole movie totally plays if Ava only has normal human-level intelligence and is just better at reading facial expressions than normal person. She's just human-level IQ that figured out how to escape because she saw this sucker delivered to her on a plate from Nathan.