As a Jewess in medieval England, Rebecca is despised on account of her rank in society, not withstanding her extraordinary beauty. She is the loyal daughter to her father, Isaac of York, a moneylender. When troubles rear up about her, she proves that although she is a pariah, she possesses a laudable amount of mettle. After being captured with her father, the wounded Ivanhoe and the whole of Cedric's household, she is separated from her father. Only by entreating an old resident of their prison is she able to attend to Ivanhoe. While doing so, she begins to fall in love with him, knowing that there is no hope because by all accounts in medieval England, he is above her ethnicity; when Ivanhoe discovers that his healer is a Jewess, he treats her with coldness inherent to his breeding and the culture of his land. Throughout the book, she shows that she is kind, ready to help and has a very humble nature.
Many readers and critics regard Rebecca as more interesting than Rowena. Perhaps it is because Scott develops her role and personality in the story, making her seem warmer and more inviting than her counterpart Rowena, who comes off as cold and pious. To amend the rather discouraging finale to the story (when Rowena marries Ivanhoe) another Victorian author, William Makepeace Thackeray even wrote a sequel entitled Rebecca and Rowena, in which Ivanhoe is remarried to Rebecca. I suppose that that is one of the advantages of fiction; you can find a way to change it if you don't happen to like the outcome of the story!