I read the title before I clicked on this thread and thought Chibi Chibi from Sailor Moon Sailor Stars :-)). Its very rare to see a chibi chibi cosplay because it wouldn't work unless the child was very young or very small. I think she would suit her quite well.
In her regular form
For her hair you could curly it then put it in bunches and put some heart clips at the top of the bunches, you could colour her hair but cause she is only little it wouldn't look like you're being lazy or anything like that :-))
She will be a little hit with anyone who has seen the show and I bet she will feel like a little princess, I would xDDD
In the name of the moon, I will punish you!
Will do commissions if anyone is interested...