Q.We are friends with another family in our neighborhood and see them nearly every day at school and at community events, but we don't socialize with them as much as we'd like.

The parents are fun, charming, intelligent people and they have three children, too. Our first two children are good friends with their first two, but our third children -- theirs is 4 and ours is 3 -- have different temperaments and are not well-suited to each other.

Our youngest would like to be accepted by this child, but she is downright mean to my daughter almost every time that they're together. She has bitten her several times and often berates her, calling her "stupid" or telling her that she isn't her friend. She isn't exactly kind to other children, either, but she most often singles out our daughter, perhaps because she is a few months younger.

When they are together, I try to be within earshot so I can remind the girls to play nicely (and let the other girl know that I'm watching). Although the mother and I disagree on how much a grown-up should step in when one child is being mean to another, she still wants to get the girls together nearly every week. It's becoming difficult to say no, again and again. I would love to see more of this family -- the fun possibilities would be limitless! -- but not if one of their children is hurting one of mine.

Can I say something to the mother and, if so, what? I wish she would just realize that these children are not a good fit and leave it alone.

A.Please do say something, but say it kindly, gently and nonjudgmentally.

That's the best way to get your friend to listen to you.

Don't bother to review past problems with her, however. If you do that, she will get defensive and you won't get anywhere. It takes an open-minded parent to believe that her darling child was ever mean to anyone, even if the behavior was blatant. Instead she will tell you that her daughter was tired that day, or she wasn't feeling well, or that she must have been provoked. Or she will say that your daughter is "too sensitive" or "timid."

The next time she wants to get all the girls together, simply say: "We'd love to do that. Just let me see if I can get a sitter for our little one."

When she asks why, tell her that your youngest and her youngest seem to bring out the worst in each other and that you want to give them a chance to grow out of that behavior. As long as you smile when you say it, and don't blame her child or yours, your friend will accept your decision. She will probably think that you're overprotective and possibly a little bit squirrelly, but you can live with that.

When the girls do play together -- and it's bound to happen sometime -- be vigilant and divert them as soon as they get testy. It will be easier to stop what you're doing and read a story to them or give them a few cheese cubes to boost their blood sugar (and their spirits) or to put your 3-year-old on your lap while you chat with your friend rather than to arbitrate a full-blown quarrel.

Learn to arch your eyebrow, too, which is one of the most potent tools of discipline a parent can use. Simply look at the difficult child with a cold eye, a mirthless mouth and a single brow raised high. This intimidates children quite nicely.

And don't hesitate to reprimand a biter or a berater, wherever you are. If you're respectful enough, or silly enough with your corrections, neither the child nor the mom will be offended.

Don't expect this child to be mean for the rest of her life, either. Insecure children often go through a mean phase in their early years, until they figure out how to get what they want in a more civilized way.

For more definitive help, see if the library or the school has a copy of a fine out-of-print book called "Bully-Proofing Your Child: A Parent's Guide," by Carla Garrity, Mitchell Baris and William Porter (Sopris West).

Questions? Send them to advice@margueritekelly.com or to Box 15310, Washington, D.C. 20003.