How did she contact this scammer? How does the scammer install TeamViewer on her phone?
Do they meet in person? Or did she install it with herself?

If she didn't meet this scammer in person there's no way that she can find this guy and you can't reverse the transaction.

No one here on the forum can able to help you or her with this case much better to report and seek help from local law enforcement or any cyber security agent that can able to track down this scammer.