What according to Lady Catherine determines whether or not two people are formed for each other?

She believes that pedigree and family connections are what make a good marriage. Lady C says that Elizabeth is upsetting high class family and friends by intruding on Mr. Darcy,

"While in their cradles, we planned the union: and now, at the moment when the wishes of both sisters would be accomplished in their marriage, to be prevented by a young woman of inferior birth, of no importance in the world, and wholly unallied to the family!"