Although I am new here, and to the field of magic(k) in general, I know that with a lot of possessions, or possible possessions, a good thing to do is to use your faith.
By that, I mean that if you are willing to attempt to combat it (probably not a great idea if it has held out and physically affected the object itself) you could at least trap it and the box within a salt circle, or with holy water. To have a magic(k)al symbol to use similar to that of a cross would work, as well, if you needed to ward them away.
If you don't want to fight it yourself, I am sure that any church nearby would have priests that are trained to exorcise such objects, and I would guess for free or for a small donation. After all, a lot of churches are intended to save souls, and preventing harm to your daughter and fiance would be a part of that.