Is it incumbent upon the daughter-in-law to treat her husband's parents as her own parents? And can she interact with her mother-in-law based on the Hadith, "Paradise lies under the feet of mothers"?

A wife is not obligated to treat her husband's parents as she treats her own, nor is she required to serve them, unless she volunteers to do so as an act of kindness to her husband. The rights of one's own parents are greater, as they are the woman's origin and nurturers. The virtue and reward of honoring one's parents are not equal to the virtue of being kind to one's mother-in-law.

The hadith "Paradise lies beneath her feet" encourages honoring the mother, and it does not mean that Paradise is literally at the feet of every mother, but rather that whoever honors their mother enters Paradise. This virtue is specific to honoring one's own parents and is not contingent upon good treatment of the husband's mother. However, whoever treats her husband's mother well will receive a suitable reward. The hadith "Paradise lies beneath the feet of mothers" is not authentically transmitted with this wording.