Yay Shimako molestation!

Actually that's Sachiko. While the hair color appears a bit brighter than normal, Sachiko's hair is straight and Shimako's is wavy. Also, the molestors are Youko and Yumi, and while Yumi has reason to molest Shimako, Youko doesn't. Not to mention Yumi has Sachiko's rosar hanging from her right hand.

The tag says it's Kanina Shizuka, actually... which makes much less sense if it's Sachiko, but more if it's Shimako.

This is pretty obviously the Rosa Chinensis group.