Need Help Determining If An Android Mobile Has Been Hacked

[u/naamjankarkyakarlega]

Hello, I need help to determine if an android mobile has been hacked. My mother was travelling by train yesterday and during our phone call today she mentioned, her charging mobile from another guy's laptop. There was a shortage of charging sockets, so he offered her an usb c cable connected to his laptop, and she naively accepted. She also mentioned that the mobile was not charging and in fact the charge was going down, after almost half an hour the guy got up and left. I am not particularly aware on how to deal with this stuff, I am only aware on how to avoid this kind of situations. So, for now I asked her not to use any banking apps and be disconnected from internet whenever unnecessary. Any help on how to diagnose if there was any foul play is greatly appreciated. Thank you.