On her computer, why not just use Thunderbird on it? Or even outlook, or whatever she likes. She just needs to pick the software.
On her phone, or even yours, why the stuff with accessing Thunderbird through vnc. Just add the server to whatever mail app on your phones?
If you want a web based thing, roundcube or sogo. But Thunderbird is gonna suck the way you are trying to use it.
Depending on what people do, the government already has their fingerprints.
Personally, I work around schools so I had to get a background check and fingerprinted for that. I also am licensed to handle explosives, both federally and at the state level. I been fingerprinted for that. I’ve gone through TSA for hazmat endorsement on a commercial driver’s license. That needed fingerprints and a background check.
Getting fingerprinted to get through airport security is the least of my privacy concerns.
But my threat model isn’t the TSA. They aren’t a concern of mine, although I do opt out of their facial recognition.
I am concerned with internet surveillance, corporate surveillance, and communication surveillance.