Tsundere group is missing Reo from Sonohana. :3
Is she voiced by the same seiyuu as these three?
You are correct. Rie Kugimiya does provide the voice for all three characters, among many others: http://en.wikipedia.org/wiki/Rie_KugimiyaStahnAileron said:
Is she voiced by the same seiyuu as these three?
Yep. If anyone, aisaka_taiga from Toradora! should be here.