Before you grab the chainsaw and go postal on the pair of them, take a deep breath and find a better, more rational way to deal with the situation

1) Make sure you have all the facts first

It's possible that you're wrong, and the two of them haven't been stealing away for chardonnay-drenched trysts at the No-Tell Motel.

What makes you think that they are? If you hate baseball and she enjoys it, maybe the fact that they both end up at the same home games is just love of the sport.

But if you discover a charge on his credit card for $200 at the local jewelry store and you birthday isn't for another six months, you're probably right to be suspicious.

What sort of a person is your friend? Is she the type to jump into bed with anyone who asks, or is she more the quiet, reserved type?

It may be painful to admit, but if she's has a history of slutty behavior, she may not see your man as off limits, no matter how close the two of you are.

What about him? Is he every bit as attentive to you as he's always been, or has that slacked off in recent months? When the two of them are together, are they flirty? Or even worse, have they started avoiding each other's eyes when you're in the room?

The sensible thing to do is to ask them, separately, if there's something going on that you should know about it.

Chances are, your guy will deny it. But if she's a very good friend, she'll most likely break down in tears and admit the whole thing. If they both deny it and you're still suspicious, you may have to do a little detective work ' as sleazy as it feels to follow him after work in the evening to see where he goes, it may be what you need to do to get the information you need.

Just be sure you're ready for the truth, because it may turn out to be something else entirely.

2) Take a deep breath and count to 3,000

If your worst suspicions are confirmed, take a step back and breathe. Try to banish all thoughts of tying the two of them to a boat anchor and dropping them off the nearest pier, and center yourself.

Go ahead and cry for awhile. Then wipe away your tears and decide what, exactly, you're going to do.

If you're brave enough, arrange for a private discussion with both of them and tell them that you know what's going on.

Ask them to explain to you what's going on. You may find out that the two of them have shared nothing more than a couple of lunches and a few stolen kisses. Or you could find out that they're having a hot-and-heavy affair. Either way, you deserve to know the truth.

But don't give in to hysteria. Tearing at your hair and shrieking, "Why, why oh why?!" won't solve anything, and you'll lose the upper hand. This is a time for quiet, seething anger.

Fix them with a cool, steely gaze and tell them how ashamed they should be for betraying you. If you feel the waterworks about to start, walk away ' a dramatic exit is always preferable to a hysterical scene.

3) So, who do you want to keep?

Sadly, this now means that one of them is going to have be gone from your life, your man or your friend.

In many ways, her betrayal is far more destructive than his ' men are known to stray, but friends are supposed to keep their hands off their buddies' husbands and boyfriends.

In most cases, women choose to try and patch things up with their partner and give the boot to the friend ' after all, you can make him go with you to couples' counseling, but they don't make "broken friendship" therapy.

If you're going to make it work with him, she has to go ' and he has to agree that he won't see her anymore, either.

But if you want to keep her as a friend, this could be a lot harder. Will you be able to trust her with your next boyfriend? Will you ever be able to enjoy her company again without thinking of what she did? Rationalizing a cheating spouse's behavior ' after all, you can tell yourself, he's just a weak man ' is easier than justifying the betrayal of a trusted friend.

In the end, you may find that you need to be quit of both of them and start over. If they get together as a couple and you run the risk of seeing them socially, you may even want to think about moving to a new city.

It's not fair, but sometimes life throws you a major, destructive curveball. But when you do start over, whether it's in a new place or in your same home town, just make sure your next new friend is someone you can trust ' and that you give your heart to a man who understands the meaning of loyalty.