Thanks for all your replies.
Firstly, I do discipline my children and I'm not in the habit of letting them do what they like, particularly hurting other children.
After the first incident, I did ask her why she didn't give me a chance to deal with things and she said she was sorry if she'd upset me, but she thought I was feeding ds. I thought that things were sorted out.
The incident with my dd, happened at my house. I think I was cooking tea at the time, there were 6 kids here, and I had missed what had happened. When I realised that dd was crying, I went upstairs and took over. I didn't say anything to my friend really, just went into dd's bedroom, asked to her calm down and then bought her back downstairs.
There was another incident at school the other day, when I had to pop in and see the teacher and my friend watched the kids outside the classroom for me. When I came out, she had dd under her arm, because dd refused to move and they needed to walk down and collect the others from the Junior School. I didn't have a problem with her physically moving dd if she wasn't co-operating but then my friend went on to tell her dd, that my dd had been really horrible, which did upset me a bit.
I know I am probably painting a bad picture of her, but she really has been a very good friend to me. She is, on the whole, very good with my children, she plays with them, talks to them and has a joke with them. She helps me out a lot in practical ways and I would probably be lost without her. I am a single parent with lots of kids, so I need a hand ocassionally.
Maybe it is the fact that we spend so much time together that she feels she can discipline them. If they are playing up then I don't really have a problem with that, I just think that on these occasions she has gone too far. I need to find a way to deal with any future incidents if they arise.
Just for the record, her dd's are not angels by any stretch of the imagination, but I just don't get so involved in disciplining them. I would certainly not shut them in their rooms.