What is Mrs.Bennet's position on Elizabeth's refusal to wed Mr. Collins? What rationale does she provide for insisting they marry, and what does this reveal about jot only her character, but about about her relationship with Elizabeth?

When Mr. Collins first brings up his proposition, Mrs. Bennet is all over it,

Oh dear! -- Yes -- certainly. -- I am sure Lizzy will be very happy -- I am sure she can have no objection. -- Come, Kitty, I want you up stairs.''

Elizabeth of course is less than enthusiastic about Mr. Collins. Mrs.Bennet's rational for this union is simply because Mr. Collins is a man of gentry and connections. His incorporation into the family gives the Bennet's wealth and social connections. Elizabeth will have none of this. Elizabeth looks for character and decency before money and connections.