She was a biter as a toddler and we keep thinking it's stopped. I think she last bit her sister about 6-9 months ago, and prior to that it was probably a year or so. But this week DH was called in by the teacher to be told that she had bitten another girl during a dispute over the slide. (DD2 says the other girl nearly pushed her off the edge at the top.)
It's very difficult to deal with in any consistent way as it's so infrequent, but she really does seem too old for this now and it's getting her into serious trouble.
It's not something she chooses to do; she just seems to see the red mist in certain situations and then is not in control of her behaviour. The rest of the time, her behaviour is normal; she's fairly quick to tears and anger but doesn't lash out very often.
We've talked to her about it, which is hard because she really wants to put it behind her, and DH has told her to walk away if she feels like that again (nice advice but I can't see it happening!). I've ordered a kids' book on anger. Any other suggestions? All the advice out there seems to be for toddlers, which makes me feel even worse!