from what i understand, she just showed him the game he comes from.

I don't understand the last panel. If I read it correctly, the small text beside his face is:

知ってるんが--
いっぱい死ぬよ?

Almost. That ん is 人.

Bad Nitori, bad! Don't show poor Ling Tong how everyone he knows dies.

That last panel makes me want to make a too much information pool.

If anything Ling Tong, you actually outlast Gan Ning.

... how did Nitori got her hand on a copy of Sanguozhi? o.O