If you saw the recent film, We were Soldiers, Mel Gibson plays the JSP part. Of course she had to enlist under a false name, and several times she came close to being found out as a female. When the US military did find out, it was hushed up and its hard to find any public record of her bravery. This teenage indiscretion is not something she likes to talk about as now the American incursion in Vietnam is viewed with distaste by most people.
She may well have taken an anti-war stance back in the swinging '60s - as did so many people - though I can find no mention of it online. In her Independent on Sunday column the only reference to that decade appears to be to the time the police found hash in her wedding cake: http://argument.independent.co.uk/regular_columnis ts/janet_street_porter/
She was more of a fashion and culture commentator on Petticoat magazine, the Daily Mail and Evening Standard before moving into radio with LBC. Why do you ask?