an abundance of mysterious people.

Standard Gothic suspense technique.
And of course there are then to two young men who pronounced Catherine to be very pretty at the end of the ball.

Can see shades of Shakespeaere in this- Romeo and Juliet, for example. But also standard romance- it happens at the beginning of The Monk -falling in love accross a crowded room.

] In Chapter 6, Isabella says that she saw a young man look at Catherine with love.

And just how many books has Isabella been reading? ;-)

This brief account of the family is intended to supersede the necessity of a long and minute detail from Mrs. Thorpe herself, of her past adventures and sufferings,(snip)

A standard technique of early novels- to have a "break-out section" filling in the lives of recently introduced characters. Don Quixote did it, Chaucer did it, It's in The Monk too.

I am sure that it's not so much a comment upon Mrs Thorpe's life as another dig at novel-writing that tries to be moralistic.

] So what could the mysterious adventures and sufferings be in reference to?

All part of the Gothic parody! I don't know if it's funnier if you take it seriously or if you do not..either way, JA is really clever!