Well, I don't think people who interfere are always bad. I mean, when the person who is being interfered to be interfered with for some sort of problem that they can't get over without someone else (drug addiction, alcoholism, etc.) then it's right to interfere.

However, if it's something as miniscule as a little high school relationship then it isn't right to interfere (unless something big is going on, such as abuse going on between them).