Under these circumstances, it appears Sun was denied the promotion because of unlawful sex discrimination. Charlie (i.e., the employer) based his decision on particular stereotypes that women with children should not live away from home during the week. Although the federal EEO laws do not prohibit discrimination against caregivers per se, the Equal Employment Opportunity Commission (EEOC) has described circumstances where discrimination against caregivers might constitute unlawful disparate treatment under Title VII of the Civil Rights Act of 1964.
Although women actually do assume the bulk of caretaking responsibilities in most families and many women do curtail their work responsibilities when they become caregivers, Title VII does not permit employers to treat female workers less favorably merely on the gender-based assumption that a particular female worker will assume caretaking responsibilities or that a female worker's caretaking responsibilities will interfere with her work performance. Because stereotypes that female caregivers should not, will not, or cannot be committed to their jobs are sex-based, employment decisions based on such stereotypes violate Title VII.
Source: EEOC Guidance: “Unlawful Disparate Treatment of Workers with Caregiving Responsibilities,” reported in Employment Practices Guide, New Developments ¶5243.