how does lydia behave when she returns home after her wedding? how does elizabeth preceive this behaviour?

When Lydia arrives home from her she hasn't changed a bit, and she treats her family who've been worried about her (physically, emotionally, and her reputation) as if everything was wonderful (Chapter 51)

"Lydia was Lydia still; untamed, unabashed, wild, noisy, and fearless. She turned from sister to sister, demanding their congratulations; and when at length they all sat down, looked eagerly round the room, took notice of some little alteration in it, and observed, with a laugh, that it was a great while since she had been there."

Elizabeth is eventually so disgusted by her sister's behavior that she leaves the room and when she returns to hear her sister behaving arrogantly to the rest of the girls because she's married first. When she proclaims that she'll hold balls to accomplish the "marriage" of her sisters, Elizabeth says;

"I thank you for my share of the favour," said Elizabeth; "but I do not particularly like your way of getting husbands."

She perceives her sister's behavior as flighty, arrogant, and inappropriate.