It's also a non-issue if you use Ubuntu like chrome OS. She doesn't have any data stored locally.

More generally, this feels roughly equivalent to saying "it's better to live in a tent than a house, because a house will crush you when an earthquake happens."

It's also very rare on Linux. On Linux, 99% of software comes from trusted repositories. The odds of randomware existing in the Ubuntu repos is low.

It's not the wild wild West like Windows. There are structural reasons why Linux desktops are less susceptible to malware, as well as the obvious marketshare issue.