how does Justine comes to live with the Frankenstein family?

From the text:

This girl had always been the favourite of her father, but through a strange perversity, her mother could not endure her, and after the death of M. Moritz, treated her very ill. My aunt observed this, and when Justine was twelve years of age, prevailed on her mother to allow her to live at our house. The republican institutions of our country have produced simpler and happier manners than those which prevail in the great monarchies that surround it. Hence there is less distinction between the several classes of its inhabitants; and the lower orders, being neither so poor nor so despised, their manners are more refined and moral. A servant in Geneva does not mean the same thing as a servant in France and England. Justine, thus received in our family, learned the duties of a servant, a condition which, in our fortunate country, does not include the idea of ignorance and a sacrifice of the dignity of a human being.