I think that your girls have very pretty and quite unusual names but that the names you listed don't fit in too well.
Nona and Piera sound international and not very english. It seems like you've heard the names in a southern-european country (Spain / Italy / Portugal) and decided that they would work really well in english. With your list it's the other way around.
Violet, Georgia are too usual and too english.
Anna - Might not be popular but also isn't extraordinary.
Freya - Nona and Piera feel very southern-european to me, while Freya is very nordic
Martha & Millecent - while old and vintage sounding they don't really match the style of your girls names.
Btw, do you pronounce Piera like the french Pierre-a or Pee-ruh?