I have been friends with this woman since our children were born. Our children went to nursery together and now are at school together, so I have known her about 7 years.
Alarm bells started about 2 years ago when they started school. She was always very quick to talk about people but I initially I thought it was just an extension of friendship to gossip a bit. However, in the past year I have had two really unpleasant experiences involving her.
The first was at ds1's birthday party. The entertainer was really bad to the point that some parents complained about her. The friend didn't say anything to me but a couple of hours after dh and I were browsing the Internet and found a review that had been written that day saying it was the worst party she had ever been to. I confronted her with it and she took it down but never apologised. I excused it as a moment of poor judgement but two weeks ago there was another incident.
This time it involved the whole class. I am on the committee of pta but she is a very vocal helper. She suggested something at the school be done one way and because I thought she was a friend (and because I thought she had a good point I decided to support her). Loads of people disagreed with her but somehow she managed to wriggle out it by saying "I completely disagree with 80s and it was her who said it". A few days later when I tried to pin her down about it she started having a go at me and telling me it was my fault (if only she knew how much grief I took on her behalf) and that I was too "controlled"
There are two issues with ignoring her. The first is our kids get on really well and the second is that we are forced together by school and share he same circle. She is charming and I think reasonably good at getting on with people. Inwardly, I am still really angry about the trouble she caused me.