Why is mr Collins offended by Lydia?

I cannot think of Mr. Collins being offended by Lydia if the moment is concerned when the girl are preparing for the first officers' ball, he rather looks confused but her inarticulate laughter might as well offend him, though I think it did not. Anyway, I find it rather hard for anyone to truly offend Collins - he's such a limy character, with overpriced opinion about himself but too stupid to take an offense other people would

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There are different answers to this question depending on whether you are referring to the book or some production.

In the book, Lydia offends Mr. Collins when he is trying to read to the family; she becomes bored and begins to engage in mindless chatter, interrupting him.

In the A&E Pride and Prejudice, Mr. Collins is offended because Lydia runs through the hallway without her outer gown on.