If youtube and e-mail is her use case, she doesn't need that crappy old Windows machine or a new $600 iPad, she needs something like a Samsung Galaxy Tab 4 (about $150) or if the physical keyboard is important, an ASUS Transformer book ($250). There are also Chromebooks from Acer, HP, Samsung, Lenovo, etc. for under $200. All cheaper than the $300 she's paying to repair the old Dell.

I think that's a big piece of what makes the original quote from Apple seem so off-putting. They don't create hardware that's at a reasonable price point for people who are struggling with their crappy old Dell and keep paying the guys at Best Buy $300 to keep it running for another year. Your MIL has a lot of good options that she could try, but none of them are from Apple, and they give no indication that they plan to change that.