Flat head

My MIL is consistently pissing me off with putting a folded up fabric around my 8week old daughter to make sure she sleeps facing the ceiling. My daughter prefers with her face to the right. It's really pissing me off because she keeps going on about how she used to put a plate under my husbands head when he was younger and he has a flat head. Is she right? Should I be concerned? My daughter has a nice round head and I want it to stay that way, not get flattened