This applies whether the package was dropped off or handed directly to you, signed for, taken into possession, or not. If the original seal is intact, the carrier must accept the refusal.
It's unfortunate that she opened any of them, because now the above doesn't apply and she probably technically took on some legal risk/liability by doing so.
Usually just because a package has been misdelivered, but you still know it's not for you, you still haven't gained the right to open it.
Still, hopefully someone will help her find a way out of her predicament.