Other children's behaviour - how to deal with it?

[surprise]

I have a friend (who is v nice) who has a ds who is 3. He is dreadful and she will not discipline him at all. basically, she very half-heartedly says, "don't do that" and then lets him continue. Last time they came to our house I ended up locking him out because he wouldn't stop slamming my back door (entirely glass and I was concerned he was going to shatter it). she still didn't seem to do anything, and I felt it was down to me, although I felt dreadful. would you do this? I've tried to talk to her about it, but she really doesn't seem to see it's a problem.

its a tough one. you dont want to offend her by commenting on her parents.

i owuld try and say "ooh it must be so hard dealing with XX" bringing up his bad behaviour but saying its a problem rather than her not coping. then maybe suggest some idea's ofaltering the behaviour. you know like "i saw on XXX that they suggested....{insert good advice}..maybe that would work"