This may be Mr. John Allen; but, if so, one wonders why he was not mentioned initially, along with the other guests. It is possible Louisa means Edward Allen; for, when reporting on the young men and women at a similar gathering (see N14), she seems inclined to avoid first names in favour of the more genteel "Miss"--and, one suspects, "Mr.," should she have chosen to name "all the young gentlemen."

And it is very possible that she means Edward's cousin (if indeed he is an Allen), with whom she may not be very well acquainted or of whom, for other reasons, she may prefer to speak in a formal manner.