It's not in the movie itself, but in the back-story used when they were developing and fleshing out the character.
I DO believe there was a scene that was cut from one of the three movies with Saavik which would have discussed it.
That's all fine and dandy, but if it didn't make it to the screen, then it didn't happen as far as the audience is concerned.
She was portrayed as a Vulcan. As a Vulcan, she sucked. End of story. IMO and YMMV.
<<Edit>> I suppose I shouldn't say
she sucked, because if she was following what the writers/directors wanted, she technically did nothing wrong.
The chick they got for the later movies was a much better portrayal IMO.