Good advice and insight from Cary and the folks. I had an experience where I dated a guy whose sister was a nightmare and sadly I can’t call her intelligent, interesting, or attractive. For a time, I actually understood her behavior because I met him through her as she and I had been friends. I figured she didn't want to lose a friend and have her bro come between us. I tried to be sensitive and put myself in her shoes; but it proved impossible with someone immature and unreasonable. We too traveled in the same circle, but after some time, I just stopped hanging out with the group and going to the family functions. It alienated me from his parents because they just couldn’t see the situation clearly even though they witnessed many of her outbursts. I always took the high road, always just ignored her, but it proved to be too much and all I could do was remove myself from the situation and preserve my sanity. The parents thought I was the bad guy. Crazy people but pardon the cliché, blood is thicker than water. Anyway, we’re no longer together for many other reasons; but the experience taught me that you have to stand up for you and/or avoid the individual. The LW’s bf, while seemingly sensitive, isn’t going to help here. Perhaps there’s allegiance to his ex and he feels he’s stuck in the middle. As other folks have stated, concentrate on socializing with your own friends. She’s an ex and not a family member, so there’s little to lose. The risk of removing yourself from the group shouldn’t be a monumental setback to the relationship. If it is, then there are other issues. Good luck.

I've been having a similar problem (the sniping, not the ex) with someone I work with. Reading the letter, and the thoughtful responses from other readers, has been really helpful in my plan for how to deal with it.

My husband's ex can be very hostile in small ways - passive aggression is difficult to deal with because, well, it's passive. And typically designed to push your button so very quietly that even you are left wondering, "am I overreacting or is she a bitch?"

I hit on a response that really works for me. When I'm on the receiving end of a subtle put-down, or come out on the losing end of a comparison, I say, "Huh - well, you win." Then I move on. Saying it like that calls the person out for trying to prove superiority, but is also lighthearted enough that others in the crowd are not made to feel uncomfortable.

I will sometimes self-deprecate: when my taste in movies or books is questioned, I say, "Yep, I'm a nerd, I've accepted that about myself" and laugh.

Both of these responses have helped to defuse the tension but also put the other person on notice that you're onto the hostility, and that you are flat-out not going to play.

I've hit upon a response that often works for me in similar situations. (My husband's ex can be very snide, and passive aggression works because, well, it's passive enough that you question your own responses.)

When I'm on the receiving end of a subtle put-down, or when I'm on the losing end of a comparison, I shrug my shoulders and say, "Well, I guess you win." Saying it that way puts the other person on notice that you are 1) onto the games and are not going to play; and 2) is lighthearted enough that anyone else in the group is not caught in the crossfire.

It also points out the absolute stupidity of the person trying to compete or prove superiority over things like schooling or movie preferences.

That's in answer to your first question: why do women do this to each other? What? You really think women are morally superior to men?

Now for the more practical advice: my sister did this sort of thing to me for YEARS. She would never acknowledge it (still hasn't). But it doesn't happen any more. Earnest heart to heart conversations did not work. Getting angry didn't work (it just gave her the opportunity to say, 'Oh, you're being too sensitive.') Ignoring it didn't work. What did work, finally, was a two-fold, good-cop/bad-cop approach:

1. I took one of her subtle jabs in public and ran with it. "You know what? You're absolutely right. That was a dumb thing to do. I did it because I am really stupid. And ignorant, too. Did you know I was ignorant? Because if you hadn't noticed, I am. I also pick my nose, cheat on my income tax and put empty jam jars back in the refrigerator. Also, I never replace the toilet paper and I have never read Moby Dick. To this day I cannot figure out why my husband married me--and oh, yeah! I'm overweight, too! I bet you left that off..." etc etc. You get the idea. Everybody was laughing except her.

2. A private come-to-Jesus session in which I told her that if she wanted to see my children on any kind of regular basis (she really adores them), she was going to cut that shit out. Period. End of story. I meant it and she knew it.

You have your boyfriend as a similar kind of leverage. Use it.

Trust me. It works.

I humbly believe that my advice is better than Cary's suggestion to give her a hearty "fuck you" because, in some circumstances, this allows the offender to get all prissy about "foul language." Dunno where this is happening but if it's in the Bible Belt, for instance, a hearty "fuck you"--even a richly deserved one--could easily backfire. Happened to me.

I'm just going to echo the few other sage letter writers who have called you on your self-congratulatory, moral high-ground crap. C'mon! You have a hand in this. Why do you insist on hanging out with this group of people, even though they're not even your friends? It sounds like your boyfriend isn't close with his ex either, so there is absolutely no reason to show up at one of her parties, unless you're being a provocateur... which, LW, I think you are.

Also, has it occured to you that her snideness might not have anything to do with the boyfriend? You said so yourself, it was years ago, it wasn't even serious, they were never fully intimate (just say they never screwed, no need to tip-toe around in). Maybe she just doesn't like you because you're annoying to be around. Hey, I don't know, I've just throwing out guesses here. She could have any number reasons for not liking you, including that you might just happen to get on her nerves.

So, I'm going to disagree with some other posters who have suggested that the boyfriend make it clear to her that he no longer loves her, that YOU are the woman in his life. Please. He'll just embarrass himself. She'll laugh in his face.

And remember, these aren't your friends, so if you slap her or tell her to fuck off you won't be seeing any of them again. They'll side with her, and see your rage as misplaced and uncalled for (which it would be). So, if that's going to be the outcome anyway, why don't you just stop seeing them before any drama ensues? Make new friends. Make new drama... because I know there is a serious drama queen lurking behind that steely exterior...