Dd is in reception and theres a girl there who dd really likes but it's pretty obvious she doesnt like dd.
My dd is quite bubbly, quite a character, chatty (non stop!!) Etc
The other little girl, who I don't know very well, is quiet and comes across.. shall we say, older than her years? Almost like "I don't have time for this nonsense" type 
Issue is, dd really likes her and I feel like it's causing her some anxiety, this other girl will play with her sometimes then ignore her other times. Even just little things like at the start of school dd will say "hi XXX!, Hi!" And keep saying hello but the other girl just looks straight ahead, stoney faced and will ignore her completely. (Whilst her mum just stands by looking on but not saying anything) And my dd looks very confused/hurt. 
Its hard to see tbh and her dad just told me today that this other little girl called dd fat, (she's not) and it's really upset dd. She was crying after school and doesn't understand why this girl is acting this way when everyone else around her loves her. It's new territory for her and I know it's a learning curve, something she will come across etc but I just feel so bad for her.
I try and say not to speak to this girl and play with her friends but it's like she wants to be liked by her so tries harder only to get the same dismissive treatment.
I know I can't protect her from this completely but how can i help arm her with ways to deal with it?