-Why people like Song would lie / conceal their identity to come to US?
Lot of Chinese people, esp among these with colleague education, and not brain-washed by government, actually think very high of US and their education system. It's not surprise a few of them would lie to get Visa. There are many online forum providing tips on how to "pass" Visa interviews.
BTW, inside China mainland, not speaking truth to government officials is not a big deal in the eye of many Chinese. In fact, being 100% truth with government officials is rare. Unfortunately, US visa officials sometimes are treated the same way as to Chinese government officials.
-Does Song have any concealed goal in US?
I do not think so. It's laughable to think Song trying to "steal" US research. Basic science research is all open. You can read Science / Nature / Cell / ... journals to know the latest research. And you can ask the authors on how to perform the experiments to reproduce their published results.
The goal of Song is almost surely personal: to get something good on her resume so she can have better career.