Why do you think the narrator still puts up with her in-laws who irritate her and who continue to visit despite the fact that Modou is no longer living with the narrator?

The narrator puts up with the in-laws for two possible reasons: One is that in her culture, the in-laws are to be respected and ultimately are the ones who pass judgment upon the widow if her husband dies before she does. If the in-laws pass negative judgment, it can affect the widow's life after her husband is dead. Also, since the narrator feels guilty about her contribution to the failure of her marriage, she may believe that if she continues to be the "good" wife, Modou will return to her.