K.U.
I don't think I would say anything to the parents, as it sounds like they won't be receptive to anything you say anyway. It also sounds like DD has a pretty good handle on things so all you can tell her is to go ahead, make new friends, and don't feel bad that this other girl can't handle it. Your DD needs to understand that the other girl is trying to manipulate her and make her feel bad about something she should not feel bad about. This other girl sounds really controlling and insecure and there's no reason that should become your or DD's problem to solve. And if the troop leaders and teachers at school are aware of it, and are willing to intervene, let them deal with it. If you want your DD to say anything, maybe it could be something like, "Wow, that's a really rude thing to say!" or "What a mean thing to say!", which puts more emphasis on the behavior or thing being said as being mean, rather than the girl herself being mean.
That's really awful that this girl would refer to another child as "chocolate" - apparently she's not being taught any good manners or social skills at home. I would just make the teachers at school aware of it and if something comes up, hopefully they can talk to the parents themselves - which may carry more weight and cause less friction than you trying to say something yourself.