Hey. When we had Jazmyne I didn't mind people calling her Jaz, but DH hated it. We named her Jazmyne not Jaz! So anyway, I can't call her Jaz coz it feel wierd for me. Everyone else does, & we don't mind anymore.
Mind you though I hated the nickname Bri - Brianna - but I was the first one to start calling her that at 4 months old. We very rarely say Brianna now.
Maybe you could just ask them to call her Annika & tell shem she's been getting confused at home?