Your "bad feeling" could be a clue from the Holy Spirit, and because the beads come from a continent where a variety of indigenous religions practice magic, it’s very possible that the beads may have been cursed or used in some kind of magic ritual.
However, as Father Gabriele Amorth writes in his book, An Exorcist: More Stories, the infestation of an object is very rare. He recommends that a person "proceed with great prudence before claiming that something is infested” (pg.159).
One of ways to determine if an object has been cursed is to examine where it came from. Were the beads given to your friend by someone who engages in the occult, ritualistic magic, etc.? As Father Amorth writes, "If a magician gives us something, it is probably infested." (Note: Infestation does not mean that the devil is in the object, it simply means that the object was exposed to some kind of evil rite, generally with the intent to harm someone in particular.)
Another way is by the effects of the object. Did your friend's symptoms begin when the beads were brought into her home? If so, has she tried to remove them from the home to test if her symptoms subside?
If one suspects that an object has been cursed, Father Amorth suggests that it be sprinkled with holy water and then burned in an open area while praying. The ashes should be thrown into flowing water such as a stream or river (pg. 160).
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