I watched the video and instantly fell in love with Indica. She is that rare thing, a British child actress who speaks clear and proper ENGLISH!
I have noticed that most of the children in British film since the beginning of the talkies to now are squeaky, squawking, shrill and mush-mouthed. Yet it is not (solely) a matter of regional differences: when the adults are speaking in a thick dialect, they are still clear enough for American me to figure it out. But sadly, there are so many adorable British children that I find completely incomprehensible.
Indica sounds very mature and has perfect control of her voice. (She was a few months shy of 12 in the video.) Of course I have to admit that her own variety of English accent (London?) is most comprehensible to outsiders in the first place. I guess that just makes me a terrible Henry Higgins snob.
(P.S.: I admit I have never seen the Harry Potter movies, so maybe THOSE children would have been understandable to me.)