I prefer RealVNC.com over Team Viewer. Register an account there. Download the Server on your Mums Macbook, run it and log into remote access with your RealVNC password.
There's a VNC Viewer, for PC,Mac and iOS. Log into that, and you will see you Mums Macbook.
I have 5 machines, 2 macs, 2 raspberry pis and a PC, all on the free tier.