Can't be certain of who the other girl is. I think it's either Mifune Miyu or Kawashima Mizuki. Both have short ponytails with brown hair and are often around Kaede.

It's based on this card - post #2498633 and I believe it's supposed to be Miyu based on the context of her being unable to handle alcohol as well as the other two, as well as a minor difference in hairstyles (KWSM's goes over her ears and is more swept).