Buy and put together the case, motherboard, HDD, CPU, RAM, and call it a day...$250-$300 (if you know how to get a copy of windows) for what you're saying your mom does on the computer. Save yourself some money from a monitor and plug the computer into a TV with HDMI, if possible.
Don't say it's hard or too much work because even if you never built one you could watch a 15 minute Youtube video that will show you just how easy it is and it shouldn't take more than an hour or two to research the components you'd be buying.