She was speaking of the Right to Equality — Article 14, ‘equality before law’, the article the chapter's own infographic (Fig. 10.14) lists first among the Fundamental Rights.
Look at what she actually claims: “the women of India are happy to step into their rightful heritage of complete equality with men in all spheres of life and activity” and “the rights of women in law will be wholly honoured in the Indian Republic”. Two words settle it — equality and in law. That is Article 14.
Tip: the same idea runs through the Preamble as well, where the Constitution secures to all citizens “EQUALITY of status and of opportunity”. In the Preamble panel of Fig. 10.16, ‘Equality’ is explained as: all are equal before the law, social inequalities have to be ended, and the government should ensure equal opportunity for all.
A fair note: more than one answer can be defended here. A student who names the wider Right to Equality group (Articles 14–18), which includes the ban on discrimination on grounds of religion, race, caste, sex or place of birth, is reading her sentence “in all spheres of life and activity” just as reasonably. What matters is that you point to the equality guarantee and quote the line that supports your choice.