I love this exchange at Lady C's.

It's interesting that you bring up Caroline's earlier talk about what constitutes an accomplished woman: " . . . a thorough knowledge of music, singing . . ." etc. As I think I mentioned earlier, one might have knowledge of these things without being able to actually do the things. I have plenty of knowledge of opera, but don't ask me to sing it! It's just barely possible that Lady Catherine does have some enjoyment of music and taste in it, but of course her bragging makes her look ridiculous: " . . . I should have been a great proficient."

So it is with her comment to Lizzy that she can never hope to play well without plenty of practice. Speaking as a former piano student, I can attest to the truth of that---and once again, JA places a truthful statement in the mouth of a very silly character. But then Lady C spoils the effect with her rudeness in offering Lizzy the use of the piano where she will not disturb anyone. Tsk.