Pretty sure you can ALSO set it so nobody can tag you but you...
Unfortunately, Facebook's changed that setting. Now, you get tagged (along with the eleventy-one notifications of tag, comment, comment, etc.) but it's not added to your timeline until you've reviewed it. At which point, you can remove the tag, unfollow the post, and hide it from your timeline.
I've got a friend who did this *all* the time and it drove me nuts. She'd even tag me on photos other people posted! Not photos of me, btw - photos of things she decided I'd find interesting. After I had trouble removing my tag from one photo, I asked her to remove it and she hasn't done it since. Before that it was umpteen times a week.
As you can tell, I find it annoying and irritating to be tagged in photos in which I don't appear. I hope your cousin stops soon, OP.