I don't know if I'm overreacting, but my DD has been in a triangle friendship since nursery, and is now in year 4. Last year my DD came home from school upset as girls x and y wouldn't play with her. I let things run and spoke to DD about making other friends and you can't always play with the same people. Girl x's mum told me my DD wouldn't let her child play with anyone else and that they needed space to play with others. Hurtful but the mum is a friend so I swallowed it and went with maybe my DD was being a little clingy. I thought this had passed as things seemed to settle down, until last weekend. My DD messaged girl x to say she felt left out at school as they were always playing with girl y. Obviously as a mum the last thing I want to think is my DD alone and friendless, although I am certain this isn't the case, as DD has lots of little friends that have come for play days and DD has been invited back in return. But for some reason x is her bff and she always gravitates towards her. I have paid more attention over the last few months and x can be quite manipulative and sly, little comments designed to knock confidence or pretending ignorance of a situation to get out of trouble, but I feel she is now getting worse and trying to cause issues in the triangle. x told y that she hoped my DD didn't tell y that x is not her friend, telling DD that she doesn't like y, and telling my DD that she wants to play with others as my DD is not letting her. I know this is not true as speaking to other mums I know DD plays with a wide range of friends at school giving more weight to x not playing with her. I don't want to interfere if I'm going to make matters worse, and being friends with girl x mum makes things difficult, any advice how I can encourage my DD to move away from the triangle without causing upset?