This time round I noticed that JA uses 'I'. She has used first person in NA and MP too.
Perhaps it is a leftover from the episolatory style that S&S originally was.
This use of first person is in CH 36;
I come now to the relation of a misfortune, which about this time befell Mrs. John Dashwood.
I always find this use of first person as very special. Sort of intimate :-)