But, really, I was never much more put to it than in continuing an answer to Fanny's former message. What is there to be said on the subject? Pery pell, or pare pey? or po; or at the most, Pi, pope, pey, pike, pit.

It looks to me as if Author Austen and niece Fanny put together a simple game of replacing the first letter of a word with the letter 'p.' Fanny must have sent on a chat in this code, and then wondered why Aunt Jane had not responded in kind.

So the translation would be something like "Very well;" or "are they?" or "so" ("no"? "do"?); or at the most, "I hope they like it."