My mom has a business and mostly uses Windows and Mac OS X; I mentioned Linux because it could help save money.
She is unfamiliar with Linux though; I gave her some basic introduction (uncertain if it’s any good, but sure), but I would like to be able to ease her into Linux if she prefers it.
Explain the concept of free software to her: that it is free to use for everyone, and reproducible in case the original programmers aren’t interested in it.
Since she is going to use it for her business, she will want to know if it can use peripherals well, which it can in most cases, and if it runs Office. The main document format of the world is .docx, so recommending LibreOffice for the regular user isn’t a good idea since the document isn’t translated well after edited by LibreOffice. I would recommend OnlyOffice - it’s like Google Docs in its features, but it works offline. And it comes bundled with Manjaro, which is an easy to use distribution.