My girlfriend thinks it's ok to allow another man to give her a shoulder massage. I think it's inappropriate. ?

Sitting with a group of friends tailgating, my girlfriend thinks it's ok for another man to give her a neck and shoulder massage. She says because he's a professional and she's known him for 20 years ( he's a friend of her ex-husband ) there's nothing wrong with it. I disagree. Am I being too insecure?