Poor, poor dd. 
She is being so good about it, she said to me "Inwardly I feel so sad about it but it's no good showing it to X"
I've advised her to try and strengthen her friendship with other girls in the class, but it's difficult because all the girls are now in friendship pairs, with dd1 the only one not paired up! She was best friends with X until a new girl joined the class in about May.