Minimal viewport design
Minimal viewport design
It makes sense to stick with Windows XP and isolate it from the internet. There’s no need to expose it if other systems are already prepared for that.
Perform a fresh XP installation, keep it updated as much as possible, apply the Embedded/POSready adjustment and further updates. This provides her with over a year to upgrade to a newer laptop. Just a note, those updates might not address every vulnerability present in the consumer version of XP, but it's significantly better than other Windows releases for that system.