I too am a veteran, and I too think that Nascar is (how my wife would say) a 'redneck' sport. But I wasn't 'surprised, nor offended that she was booed.
Not to be stereotypical, but I would bet that the majority of the booers were from the same box of recycled pencils (if you know what I mean) This could have been a Dale Earnhardt memorial tribute and Id be willing to bet that if she made the same appearance the result would not have differed.
Its no disrespect to the Vets - Just 'its all about me in the here and now' mentality. Its nothing personal at least not towards the cause, only the individual and what she stands for.