I'm a 35-year-old woman who's been married for a year to a 70-year-old man. My husband's closest female friend is also one of his exes. He's known her for 40 years. She's a real sore point for me. She stayed at our apartment while we were away. She wouldn't reply to any of my emails but constantly emailed my husband. Recently, I saw a text my husband sent telling her to just email him at work because I have access to his phone. (That's how I discovered that she was dissuading him from fixing things with me when we were fighting.) I feel that a husband shouldn't have marriage-undermining friendships. I want him to stop talking with her. Am I wrong here?

--Angry

Take a counterintuitive approach and put yourself in this woman's shoes: Where's she supposed to shop for men...the cemetery?

Older women get seriously annoyed at how men their age -- typically the wealthiest and most eligible -- dip down through the decades for partners. On dating sites, even a 98-year-old man in an iron lung will set his age preference at 18-30, just in case some woman is "open-minded" (uh, about dating a man who has socks far older than she is).

Another thing to consider: In a relationship, it's common to ask for and expect sexual fidelity. But how much social fidelity is it reasonable to expect? The notion that a relationship involves becoming somebody's "one and only" socially, too, sounds romantic but is actually in sharp conflict with the complexity of many people's lives. Your husband, for example, has had a friendship with this woman for 40 years -- five years longer than you've even been on the planet. His cutting her out of his life would mean cutting out somebody who understands who he is and where he's been in a way few people probably do.

That said, it's natural that you'd wish he'd give this woman the heave-ho. The jealousy that gives rise to feelings like this is wrongly maligned as a "bad" emotion. However, like all emotions, it's actually "adaptive" -- which is to say functional. Evolutionary psychologist David Buss explains that jealousy seems to have evolved to protect us against threats to our relationship -- alerting us to possibilities that our partner will cheat on us or leave us for another. But jealousy can also be toxic to a relationship and damaging to the mate value of the partner who expresses it. (Nothing like endlessly fretting to your mate that he could trade up to suggest that he should.)

Additionally, consider how counterproductive it often is to tell somebody what to do. The late social psychologist Jack Brehm came up with the term "psychological reactance" to describe a motivational state that automatically rises up in us when we feel our freedom to do as we choose is threatened. Basically, the more somebody tries to control our behavior the more we want to resist, rebel -- do whatever they've been trying to stop us from doing. (In short, nothing like being shown that there are straps to put someone in a mind to gnaw through them.)

This isn't to say you're necessarily off base about this woman. Chances are, she resents you and is trying to chip away at your bond with your husband. Rotten. However, as for how successful she could be, do you think your husband married you by accident? Like maybe you just happened to be in the passenger seat when he pulled into a drive-thru chapel: "Oops. Thought this was a car wash."

As annoying as it must be to have this woman lurking around the borders of your marriage, consider the thinking from psychologist Erich Fromm that love is not just a feeling but something you do -- sometimes by being a little more generous than you'd really like to be. This isn't to say you have to shut up entirely about this woman. You can be honest with your husband that you find her undermining.

Ironically, the best way to control your romantic partner is not by trying to control them but by being so loving, supportive, kind, and fun that it would be idiotic for them to leave you. Also, let's quash any fear you might have that this woman could steal your husband. There's little novelty (and thus little excitement) in getting together with somebody one's known and been in touch with for 40 years. Also, recall how men, throughout their life span, tend to be most attracted to the younger ladies. Chances are, if he were to suddenly develop a thing for anything "midcentury," it would be something like Eames chairs -- not a woman who's aged out of every dating program on TV, unless, of course, you count "Antiques Roadshow."