No direct experience, but I have found the ground operations of United in PEK to be pretty good. I was once contacted by them on the belief I had left an iPhone in my seat. Wasn't mine, but the personal contact made a good impression. I also received personal contact after a highly delayed departure from Beijing, including responses to check in time. Long story short, I think the ground staff in Beijing will be good at handling this.

That said, I have no idea what will happen in Shenyang. Once the bag is on the flight there, it will be in Air China's hands to deliver it, and I have no idea how that will be handled. If she doesn't speak Mandarin, I suggest having her identify someone who does as a point of contact in Shenyang (hotel, local business/personal contact) because I am guessing that ground staff in Shenyang won't have the best idea as to what to do.

BTW, the whole thing seems slightly odd -- the flights from ORD and IAD arrive at about the same time in PEK--I'm surprised that the indirect route didn't get the bag there.