This is something that happens on its own. Sometimes it is best to stay away from the person and let them get what is coming to them. All that they send out will eventually come back one way or another. For all you know it is already happening in ways you do not see.
Those people above me is right. Just to let you know that everything happens for a reason or two. So does karma. Whatever you do, which is bad, good, or in the middle, it happens because of whatever action causes it to be so. But karma is an unbiased force that doesnt act on judgement of good or evil, yet it just whatever comes out from one end of the tunnel to another.
So just let things be. No need for spells in this matter. It would use up unnecessary energy than need.