This an an example of<em> </em><em>discrimination by sex</em>.
Explanation:
<em>Sex discrimination is the situation where someone is treated unfairly </em>as a result of the person's sex (that is, either being a male or female). It could be direct or indirect. Also, happens to be one of the <em>worst form of discrimination which could occur virtually anywhere from work place to education.</em>
What Sonja experienced is <em>a discrimination by sex</em> on an employment sector and it is quite unfortunate situation.