She wants to re-establish her superiority by hinting to you that your opinion is not relevant.
Your offering help reminded her of her inadequacy, which led to fear. Fear in turn led to anger.
In an office, do not offer help unasked unless you are the boss. When asked for help, it's better to start with exploring the problem until she gets her own answer, rather than telling her the answer out right.
(Her behavior may not be all conscious, or just reflexes learned since childhood, in order to regain her inner balance. People do things because who they are, not because who you are.)
