Catherine is briefly worried Mr Tilney loves someone else (only in the adaptation, not in the book)
In the novel when Catherine sees Miss Tilney with Mr Tilney she “immediately guessed (her) to be his sister” thereby (as Austen disappointedly points out) not having a dramatic moment of “turning a deathlike paleness and falling in a fit on Mrs Allen’s bosom.” Considering what other ideas Catherine has during the course of the novel, it’s a big deal to show so much maturity and sensibleness.
.. it had never entered her head that Mr. Tilney could be married; he had not behaved, he had not talked, like the married men to whom she had been used; he had never mentioned a wife, and he had acknowledged a sister.”
-Jane Austen, Northanger Abbey C8
The lyrics fit so well here, she’s devastated thinking Mr Tilney is in love with someone, then the moment she realises the lady is his sister the night is sparkling again. (I should probably use this song for her meeting Mr Tilney at some point)
If you’d like to discuss Austen with me book a read with me session
Audio from Enchanted TV by Taylor Swift
Video from Northanger Abbey 2007