I think that Sakura is injured because she was linked to those small slugs that were draining her chakra... The shinjuu got her chakra through the small slugs since Sakura was using a remote controll on her.
That's why she's holding his stomach (if you see well, you'll notice that her left hand is on her stomach)....Didn't the stomach is the storing of the chakra in each ninja?
That does make sense. Well in my review, I only guess, but hopefully, it will be clear in upcoming chapters. If that is the case, then it makes sense and it's sad for the heroine to feel this pain of loss. The chapter was really the downfall of our heroes.
Next chapter will explain what happened to Sakura
Hopefully.