Here's one line from each of these chapters, but there are so many good lines, that it is hard to make a choice:

1 No one who had ever seen Catherine Morland in her infancy, would have supposed her born to be an heroine.
2 'No more there are, indeed. - How very provoking! But I think we had better sit still, for one gets so tumbled in such a crowd! How is my head, my dear? - Somebody gave me a push that has hurt it I am afraid.'
3 'I have hitherto been very remiss, madam, in the proper attentions of a partner here; I have not yet asked you how long you have been in Bath; whether you were ever here before; whether you have been at the Upper Rooms, the theatre, and the concert; and how you like the place altogether. I have been very negligent - but are you now at leisure to satisfy me in these particulars? If you are I will begin directly.'
4 'What a delightful place Bath is, and how pleasant it would be if we had any acquaitance here.'
5 Alas! if the heroine of one novel be not patronised by the heroine of another, from whom can she expect protection and regard?
6 'I will read you their names directly; here they are, in my pocket-book. Castle of Wolfenbach, Clermont, Mysterious Warnings, Necromancer of the Black Forest, Midnight Bell, Orphan of the Rhine, and Horrid Mysteries. Those will last us some time.'
7 'Udolopho! Oh, Lord! not I; I never read novels; I have something esle to do.'
8 'Indeed he is, Mrs Allen, I must say it, though I am his mother, that there is not a more agreeable young man in the world.'
9 'Yes, I fancy they are, but I am not quite certain. Upon recollection, however, I have a notion they are both dead; at least the mother is; yes, I am sure Mrs Tilney is dead...'
10 'You totally disallow any similarity in the obligations; and may I not thence infer, that you notions of the duties of the dancing state are not so strict as your partner might wish?'
11 'Oh! that we had such weather here as they had at Udolpho, or at least in Tuscany and the South of France! - the night that poor St Aubin died! - such beautiful weather!'
12 'My dear, you tumble my gown.'
13 'Open carriages are nasty things. A clean gown is not five minutes wear in them...I hate an open carriage myself.'
14 'The nicest; - by which I suppose you mean the neatest. That must depend upon the binding.'
15 Here Catherine again discerned the force of love.