Thanks for the advice, yeah it's definitely intended to last a few years.
I think the current CPU in her machine at the moment is a one of the Core i7's from around the time the i7 920 would have been released, so I think thats around 10 years old.
But yeah, she's a light user and mainly uses it for browsing, light gaming or movie watching etc... These days its all about tablets/mobiles
So I'm really trying to get the balance right between spending the right amount of money that it can last for a good period of time for her, and that offers good performance as well without breaking the bank.