well maybe your cousin could use a walker and someone to encourage her to walk into the closet, has she no one there ?
My cousin is 78 yrs old & has started walking backwards usually in the afternoon or when she is tired. She has fallen in her closet because of this uncontrollable act and cannot seem to stop herself unless she grabs om to something or sits down.
My son is 19 months and does this all the time. He has since he was about 13 or 14 months. My husband and I joke that he is moonwalking. And Margy is right..distraction. It works well. I am pretty sure this is all very normal.
Walking backwards is normal very often they do this around 18 months , distraction I have found works better than anything for a tantrum at this age , wisk him up for a dance , let him watch Mom dance around the room to music, heck its also great exercise,anything that will turn his mind away from what upset him ...and even let him wail he will get rid of his frustration .