Rashi implies earlier (quoting Ta'anit 10b) that the family of Ya'akov was not affected by the famine, and they went down to Egypt to buy grain only so they would not attract negative attention from the surrounding people (who were going hungry). Since Ya'akov's family was not suffering from the famine, it was perfectly permissible for Levi to conceive a daughter.

Yaakov's family wasn't subject to the famine. He had plenty of money and was in the process of purchasing grain, which was for sale to the public, from Egypt when Joseph revealed himself. Perhaps if he had no more money or grain was no longer for sale it would have been forbidden.

Furthermore, there are commentators who posit that Yaakov miraculously had plenty of food and only sent the brothers to purchase food so neighbors won't be covetous of him.

Yaakov's family wasn't subject to the famine. He had plenty of money and was in the process of purchasing grain, which was for sale to the public, from Egypt when Joseph revealed himself. Perhaps if he had no more money or grain was no longer for sale it would have been forbidden.

Furthermore, there are commentators who posit that Yaakov miraculously had plenty of food and only sent the brothers to purchase food so neighbors won't be covetous of him.

Rashi implies earlier (quoting Ta'anit 10b) that the family of Ya'akov was not affected by the famine, and they went down to Egypt to buy grain only so they would not attract negative attention from the surrounding people (who were going hungry). Since Ya'akov's family was not suffering from the famine, it was perfectly permissible for Levi to conceive a daughter.