You can't know for sure. However, you can block, return, or remove a curse and then create a protective ritual. It means you'll have to do a little witchcraft of your own.
Alternatively, you can just ignore her and assume that such spells do not work. Remember, also that any 'bad energy' that anyone directs outwards, inevitably comes back to bite them eventually. Hatred hurts the hater far more than the hated.