is the woman planning on selling the tree for lumber use? if it were killing a tree or making it look ugly i would say you have a gripe. i dont use screw in tree pegs but have seen enough bad pruning jobs and such to know it takes alot to kill a mature tree. a couple of tree pegs wont do it from what ive seen. my old tree climber would scar a tree but in a year the tree healed nicely. i dont like doing any damage but i dont see the harm in using bow hangers or hooks to hang gear. maybe a tree expert could jump in and weigh in on the subject.