Sponsoring Parent - what happens if my mom changes country while waiting?

[kestrul]

I have applied to sponsor my mom in January 2014 in Toronto, in April 2016 I was approved as a sponsor, but there is no more news since then. My mom is aging and getting lonely in Ukraine, but she doesn't want to come to visit because she is "waiting on papers". What happens if she moves to Russia to my brother and changes her citizenship from Ukrainian to Russian? This will take about 3 month. How it will affect the paperwork? I will have to send correction to my application with her new address. Do I need to do anything else? Will she have to get the police check from both Ukraine and Russia? What happens with her health check? I guess she will have to do it in Russia. Is there anything else that we need to consider? Thank you very much for your advice!