Lizzy, in Pride and Prejudice, P&P, is nothing if not passionate when she reels against Lady Catherine de Burgh's admonishments. When she tells her that she has nothing more to say to her and must beg to return to the house, it is tantamount to social suicide.
In fact it is just what a young Catherine Earnshaw would have done in Wuthering Heights. Similarly Lizzy's refusal of both Mr Collins and Mr Darcy showed that Elizabeth Bennet was equally willful, refusing to bend to her mother's will.
And then we have the Dashwood girls, Marianne and Eleanor, who resemble something like the two sides of the same coin, one being wildly passionate and carefree, the other being more sensible and cautious in all things.
Here, with these two characters Austen openly debates how difficult it was for women of her day to deal with emotions of passion, and yet display the decorum that society insisted upon. And here we have a crucial point. The careless passion displayed by both Cathy and Heathcliff in Wuthering Heights, for example, or indeed by Rochester and to an extent Jane in Jane Eyre, was only possible because they were living in secluded rural communities in the middle of nowhere. Austen's heroine's on the other hand have to contend with life altering passions and emotions in the midst of society, be it in London, or in Lambton.
A similar situation arises for Marianne Dashwood, who must suffer the consequences of exposing her emotions too freely. She actually comes close to death, her spirits having been brought so low by her uncontrolled passion for the inconstant Willoughby. So it could, in fact, be argued that the heroines in Austen's novels are just as passionate as those in the Bronte novels, suffering equally for their passion. Just because Austen's characters must display decorum, it does not mean that they do not or are not capable of, feeling passion.
As Austen sees it, you may feel the passion, but must learn to control it. We know this because of Austen's depiction of Marianne Dashwood, who lives to regret her unbridled display of love for Willoughby.