Why do Jane, Lady Catherine, and Wickham have such negative reactions when hearing of the proposed marriage of Darcy and Elizabeth? What do their actions reveal about each character?

Once Elizabeth shares news of her engagement with an incredulous Jane. Elizabeth has to convince Jane of her feelings for Darcy. Once Jane realizes her sister is sincere, she is extremely happy.

Lady Catherine is angry about the engagement between Darcy and Elizabeth and feels it's inappropriate. 

Wickham hates Darcy, but now continues to have hopes that he will help him. He bore with philosophy the conviction that Elizabeth must now become acquainted with whatever of his ingratitude and falsehood had before been unknown to her; and in spite of every thing, was not wholly without hope that Darcy might yet be prevailed on to make his fortune. The congratulatory letter which Elizabeth received from Lydia on her marriage, explained to her that, by his wife at least, if not by himself, such a hope was cherished. The letter was to this effect: