Austin had the right to engage Ellen in marriage. The story stands on the element of plot. Characterizations are weak and depend upon artificial "tag" elements that distinguish them without drawing out any human verisimilitude.

'Oh no, people can be frightful!' Miss Scrimshaw asserted, rather flat, but surprisingly loud.

Let us begin with a summary of A Fringe of Leaves before we attempt either critical analysis or character sketches.  This is a very long novel (albeit still a page-turner) that is a historical romance with two parts:  the first is a love story brimming with guilt and the second is story of slavery and escape.  These two parts are connected by a shipwreck. 

First, to explore the love story full of guilt.  This is a true historical romance set in the Australia of the early 19th century.  (In other words, a newly settled Australia ripe with seedy characters originally from England and Ireland.)  Most of Australia, at the time, was not yet conquered and full of the native population: Aborigines.  Even the Irish and English settlers were a rough crowd, most of them being convicts and such.  What transpires is a romance between a strong young woman and a smart, more elderly man.  

Then comes the shipwreck of the Bristol Maid returning to England.  It wrecks on the Queensland Coast with Mrs. Roxburgh aboard.  She is immediately taken prisoner by Aborigines.  All Ellen Roxburgh wants is to escape, but she is ever so torn.  She feels loyalty to her dead husband, but now feels loyalty to her rescuer.  She also feels loyalty to her own class in England, but also to her new adoptive class of settlers.  This novel is the story of Ellen Roxburgh's survival.  It is about Ellen's inner struggles and how she overcomes them. 

In conclusion, we should also realize that even though this novel was written in the latter part of the 20th century, it reads like a Victorian novel (and is meant to).