It's not vindictive to use what's at your disposal to get your point across to her that she is NOT wanted in your relationship. It's protecting YOUR territory...standing up for YOUR relationship...ensuring she backs the he!! off!
Vindictive is IMPO, doing something to her after the fact (once she backs off.)...THAT would be vindictive; as NOPs already said "revenge", this is not revenge. This is her incentive to stay the he!! away from YOUR husband.
