I must be a romantic because in the passage where Marianne's talking about the falling leaves, she's describing how I feel many times when I'm experiencing the beauty of nature.

Thank you Anselm for all this interesting information. BTW, I looked up the Cambridge Austen you mentioned in another post, and all of it is prohibitively expensive. I will just have to learn from you all here.

I'm wondering if there is an overlap in romanticism and sensibility as movements.

Here's from Henry Hitchings afterword

To Austen's audience, any mention of sensibility would have been topical and provoking. Her readers identified sentiment with sociability, yet also associated an excess of it with sickness. The Irish politician Edmund Burke articulated the age's new esthetic values in an essay entitled A Philosophical Enquiry into the Origin of our Ideas of the Sublime and Beautiful (1757). Burke argued that taste was crucially linked to 'sensibility,' and that the civilized mind had to be amenable to 'the pleasures of the imagination.'

Hitchings linked Burke's writing to sensibility; but in Peter Conrad's intoduction (quote below), he seems to be linking it to romanticism too. Whether this is the same piece or writing to which they're referring, I don't know.
"In poetry a theology, romanticism is in the novel an exacting code of conduct, a rigorous decorum which insists, as did the prodigies of Burke's sublimity, that humble human individuals should fret and strain to equal the challenge of an awesome, exhilarating nature. Marianne turns the effusions of sensibility into a system of manners, and is unforgiving in her judgment of those who have not mastered its regulations, deprecating Edward for not taking pleasure in drawing or picturesquely dirty lanes....
She is a disciplinarian, demanding correct responses from herself and others,...with an inflexible concern for propriety which is closer to the logicality of sense than to the spontaneity of sensibility.

Many times I think Elinor is in fact the more feeling of the two sisters. Marianne seems express more feeling than she truly feels, and Elinor feels more than she expresses.

Anyway I found the Burke essay online. I read some of it, and if as he says pain is pleasure, then I enjoyed it.:-) Maybe I just need to try again later. But I found a section I will link below that seems to fit Marianne. You can click on book contents on the top of that page if you want to read more sections.