Is a wife obligated to obey her mother's request to prepare food while breastfeeding her daughter, even though this might harm the infant who needs to be held upright after feeding due to reflux? And is she sinful if she prefers to stay in her own apartment and visit her mother instead of residing with her due to her discomfort?

It is recommended to be kind to one's mother and honor her due to the great reward in it. However, it is not obligatory to obey her in matters that harm the questioner or her daughter. Nor is it obligatory to reside with her; rather, it is permissible to live in her house and visit her. It is recommended to strive in honoring her and being kind to her, and not to anger her, even if it is at the expense of the questioner's comfort, seeking the great reward and recompense.