A 72-yeаr-оld wоmаn with multiple sclerоsis reports 4 fаlls in the past month, all occurring when she was bumped or jostled while standing in line at the grocery store. She did not take a corrective step during any of these episodes. Her BBS is 44/56 and her Mini-BESTest is 18/28, with the lowest scores in the reactive postural control domain. Which intervention is MOST directly targeted to her primary balance deficit?