By now Catherine has finished reading 'Udolpho'.
I have to say that there are parts in it which are rather creepy and spooky (and I am a grown mature woman). I can imagine its impact on Catherine.

CH 17;
Its long, damp passages, its narrow cells and ruined chapel, were to be within her daily reach,

Emily in 'Udolpho' is informed about this ruined haunted chapel on arriving;
'They say, too, there is an old chapel adjoinig the west side of the castle, where any time at midnight, you may hear such groans!-it makes one shudder to think of them!-and strange sights have been seen there___'
She has to go to the vaults under this chapel for her aunt's funeral. I found it quite spooky here.

Northanger Abbey has a part that is decayed. How thrilling for Catherine. If she's lucky this might be haunted too.

CH 17;
.. some awful memorials of an injured and ill–fated nun.

This ill fated nun in 'Udolpho' holds the key to many mysteries and secrets.
She haunts the castle of Udolpho, has her picture hanging in one of the neglected rooms, Montoni had proposed to her, she is a nun in France, is indirectly responsible for a murder, has the picture of Emily's aunt in her little box, and is described as;
..she has no meaning in what she says. Her intellects are at times deranged.
It seems nuns were quite a part of the 'gothic' mystery and intrigue.

An abbey like Northanger 'must' have had nuns, and there has to be some legend regarding one such nun - don't they all?

Catherine can't wait to discover such delicious things that are connected with old buildings.

Here, I am quite sure, that the reader is also being parodied along with the 'gothic' novel.