re: who she is - Jeanette Winterson is a British writer, and a pretty successful one - she was awarded the Order of the British Empire for services to literature. Probably her most famous single work is "Oranges Are Not the Only Fruit", a semi-autobiographical story about growing up gay in a tight-knit religious community.
As is mentioned below, she's talking only about Kick-Ass in that comment, although another guest suggests that this is par for the course in comic books, which I think is a little unfair to comic books as a whole: Millar's doing something specific in KIck-Ass which is more extreme than the settings or action in other comic books.
However, she has read and enjoyed Dykes to Watch Out For and Paul Auster's City of Glass, so she's not down on all comic books. And, during the 30 minute programme, she certainly wasn't down on all the geek culture under discussion - she really enjoyed District 9, for example.