The reduction of Microsoft support shouldn't have a massive impact on your Mom, unless she has sensitive information stored on her machine or uses it for card purchases then the risk posed by malware is minimal. Like you I've been a user of Linux for around ten years and converted many people to using Linux. Sometimes this is not appropriate though and this is one of those cases.

It's all well and good talking about different versions of hardware but most people first become aware of alternative OSs when they already own the hardware. If they already have a 'Windows machine' then they will be blocked from installing Linux or any other operating system and they aren't likely to buy into something they don't know about when they buy new hardware. I am a die hard Linux user but would never have become one had I not been able to run a kjve distro,and install it on my existing machine

Burglary tends to be an opportunist crime. The criminal only has to walk round a wealthy area to know that most people in the houses have a large amount of valuable equipment in their houses. People should be aware of posting when they are not going to be at home but photos with geotags only convey historical data "This person was abroad on this date" and does not give away times in the future when they are going to be away.