What is the motive of jalil's wife in finding a suitor for mariam ? why does jalil go along with the plan ?

The theme of shame is explored through Jalil as he casts Mariam out of his house during the darkest point in her life. His other wives are putting pressure on him to do this.  Not only does he send Mariam out of his house, but he sends her to a whole new city, which allows Mariam to symbolically disconnect from him. Jalil speaks and acts in a manner that suggests some regret for his actions, though his feelings of paternal responsibility can not overcome his feelings of shame and the pressure put upon him by his wives.

Mariam is given no choice whatsoever in her marriage, but rather it is forced upon her. She is young and scared, and she is clearly not truly in love with Rasheed. Afghan culture, however, does not equate marriage with true love, but rather with convenience and necessity. Mariam’s role is clearly defined by Rasheed when he asks her to “act like a wife.” He demands that she clean and cook, and he will ultimately require her to participate in sex that he forces upon her.