Maybe JA is showing us that Mrs, Morland, like her daughter Catherine, begins to suspect things happening in real life just because she has read them somewhere.

Maybe Catherine inherited this character from her mother ;-)

On the other hand, I do see Mrs. Morland's POV.
Is Mr. Homespun a real person writing this on personal experience under a pseudonym? That is the impression I get.

If he is then I think such the danger is real too.
In fact I think even without Mr, Homespun's personal experience we can fairly recognize such a problem in real life.

I would certainly be very upset if my daughters dressed up in a fashion most unsuitable or slept till noon, because that was the thing with the fashionable crowd etc. etc.

Of course being country folks it can get more difficult.

But happily, for all concerned, as well as the reader, this malady wasn't there and so this article wasn't needed as a cure.