While much has been made of this Southern Drawl adoption, it should be noted that The Little Missus was reading from a text of the time. The question is: if she were speaking to a group of hmosexual men, would she adopt a lisp? Who is she, really?
Selective editing was employed to play up the pandering aspect of her speech, but Mrs. Bill Clinton deserves to be judged upon her merits - or lack thereof.