Keep an eye on the dell outlet. Theres some nice machines there for $250 now but you'll see some smatterings of sub $200 machines from time to time.
I was figuring that machine is probably 8-9 years old, perhaps more. The power supply might be getting tired, fans might be about worn out, etc. It'd stink to throw money at a special printer just because it has a parallel port on it only to have the computer crap out on you six months from now.
If you're going to need to change the monitor at the same time, a nice discount laptop instead of a laptop/monitor combo might suit her and end up being cost effective. My dad and my MIL both loved going from a desktop to a laptop, if for nothing else to be able to sit with it wherever they wanted.