I posted previously about a classmate "stalking" my ten year old DD. Thankfully, the girls have now resolved the issue with some help from the teachers and my DD is feeling much better.
However, the girl's mum took the whole thing very badly and she has caused a couple of ugly scenes in the playground, yelling at both DD and me. She utterly rejects my DD's version of events and considers that my DD was bullying her daughter. She has been very regularly in contact with the headteacher too apparently...lord only knows what she has said about us to them!! She told, well shouted, at me a while back that she was going to "take things further" with the school. I don't know exactly what that means but the school subsequently asked me to confirm that we believed they had followed their behaviour management policy in dealing with the issue (we said yes, we're perfectly happy with the process and the outcome.).
Since then I have heard nothing more although DD has recently noticed that staff are still watching her closely during playtimes and asked me about it. I just said they watch the play to keep everyone safe.
Today - weeks after the girls have resolved it all - she parked outside school and stood on the pavement watching my DD playing for the whole of morning break. DD smiled broadly and waved 
- attagirl! - but said she was frightened. I double checked repeatedly that she wasn't watching her own child and DD said no, definitely watching her.
DH says I should ignore as it is a one off and he thinks I have already got too involved... basically I think he thinks I'm getting neurotic/paranoid/too like my mother. But I feel uncomfortable, like we're just allowing this woman to intimidate us and modelling to DD that she shouldn't expect us to keep her safe.
What would you do?