Because of the differences in their social status to Robert/Travis', they cannot conceive of Harriet/Tai's attraction to and ultimate love for him, the one due to his wealth and the other due to his habits. This change is necessary for the sympathies of the audience to remain intact. Had Cher objected to Travis simply on the grounds of his financial standing, the audience would not have any sympathy for her. But because he is a stoner and somewhat stupid, her desire to find Tai someone better makes some sense. In Austen's time, class and money were everything; people could be cut off for marrying beneath them, so such a seemingly shallow stance on Emma's part would have been not only understood, but expected.
Character is by no means the only -- or even the most important -- adjustment that Heckerling made in adapting Emma into the movie Clueless. The entire method of narration is switched. Jane Austen wrote Emma in the third person, and Clueless is narrated in the first person by Cher. There is definitely some aesthetic reasoning behind this; the disembodied voice of a third-person narrator would have done much to pull the audience out of the story, as opposed to the instant personal connection established by Cher as a first person narrator. Many of the films comic moments come from this narration, as well, such as Cher interrupting herself when she spots an outfit she likes in a window (Heckerling, 1995). Even this comedy and sense of style is a necessary adaptation. Standing out was not a good thin two hundred years ago in England; it still isn't in many parts of the world. America in the nineties -- and today -- celebrates individualism, and the narration of Clueless needed to reflect that to keep it believable. "An emphasis on performance, or what we may generally call personal style, leaves little room for manners as conceptualized by Jane Austen" (Macdonald, 217).
There is still another, deeper reason for this change, though, which makes it less of a shift than it appears. Lindsay Green notes that, despite the strictly third-person voice of Emma, "both stories are told through the main character and follow her development" (Green, 124). Both stories start with a disruption in the world of the heroine and culminate in her fulfillment; despite the difference in voice, both are personal stories. Austen manages to convey this sense of the personal without forcing the reader into the "I" perspective of the title character. In film, the audience is at an automatic remove already. Unless the whole movie were shot from Cher's perspective, as though the camera were looking out of her eyes, there is no possibility of creating a true first person narrative. Thus, the audience is able to add their own analysis to Cher's observations, just as they can with the narrator's in Emma.
Though there have been more strictly faithful film adaptations of Emma and others of Jane Austen's novels, few were as enjoyable or as authentic for modern times as Amy Heckerling's Clueless. The updating and adapting she did to make the centuries-old novel work as a modern movie might strike a not of discord with certain purists, but her efforts recreated a work the spoke to Heckerling's time in the same way Austen spoke to hers. No work can ever truly be timeless on its own; it is the success of its adaptations that truly determines its greatness.
Austen, Jane. Emma. New Milford: Toby Press, 2003.
Green, Lindsay. Emma, by Jane Austen, and Clueless, Directed by Amy Heckerling. Sydney: Pascal Press, 2001.
Guney, Ajda and Yavuz, Mehmet Ertug. "The Nineteenth Century Literature and Feminist Motives in Jane Austen's Novels." New World Sciences Academy, Vol 3, Iss. 3 (2008). 523-31. Accessed via Ebsco Host 9 November 2008. http://web.ebscohost.com/ehost/detail?vid=11&hid=6&sid=49eaeb54-778c-4498-ba7a-4cd389bb44d2%40sessionmgr104&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=a9h&an=33019184
Macdonald, Gina and Macdonald, Andrew. Jane Austen on Screen. Boston: Cambridge University Press, 2003.
Southam, Brian. "Jane Austen." British Wirters, Vol. 4 (1981). 101-24. Accessed via GaleNet 9 November 2008. http://galenet.galegroup.com/servlet/Scribner/hits?l=8&t=KW&s=3&r=d&locID=txshracd2506&o=DocTitle&c=2&n=1&UZ=SWSO&DT=Biography&NA=austen%2C+jane#SourceCitation