I’m not crazy about the idea of posting those pictures… my approach would be to respond with simple, factual statements. Don’t get drawn into tit-for-tats, just say the one thing and stop following the comment if possible. I think people who post the truly nutty anti-Obama stuff are not going to be convinced with reason, so my tactic is generally to show that theirs is not the only opinion and leave it at that. If you just want to yank her chain, there will almost always be an opposing 4-chanesque poster to be found for any statement, but the risk is that it will make her just that much more hostile to people she already disagrees with.