privacy on a local network is an excellent use case for a virtual private network (vpn). your network traffic between your computer and the provider will be encrypted. i’d also look into dns-over-https, which will also encrypt your dns record requests. if everything is set up properly, the only things visible from the home network will be encrypted dns record requests out to your dns provider, and encrypted traffic to your vpn provider and back. however, with the virus on your mothers computer, i would consider the whole network compromised. you can try and harden against local intrusion, but using a vpn will not protect you from a virus, only prevent it from knowing about your traffic if its sniffing from another computer.

if you’re intending to seed with a decent upload bandwidth, you’ll likely need a vpn with port-forwarding capability. there are fewer and fewer providers these days with that offered as a service, so make sure before you sign up.