I don't know who the two blue-haired girls are. The source isn't tagged with Cirno and I've seen that same character in other images.

The one at the upper left corner is a sunflower fairy.

The relevant tag for the other one seems to be 雨の妖精, which translates as something like "rain fairy" when I run it through Google translate. A lot of the Pixiv posts with that tag have her holding an umbrella.