Same crap happened to me and Im an old coal guy who knows better (so don't feel bad).
What appears to be a pretty good option to me is the Leisure Line WL-110, It would give mom the oil back up incase you went on vacation, Its as less expensive new as any similar product of its kind and though I have not had the opportunity to have/use one it does have the critical sections brought in from AA which speaks to its quality, I do know the owners of this company are very approachable, honest and helpful regular folks who enjoy trying to help others (be it an old lady or a new student or anyone in-between).
You should call them and ask the pricing or any senior discounts at 570-752-1811
EDIT: Flyer posted as I was typing
^^^^ Flyer dude who posted above is a LL rep, he can help you
EDIT2 (Dave how about you take one of your spankin' new AA pressure vessels and throw it on a WL110 and give the woman a 10% Senior Discount
) This lady would pay for that unit in 3 heat seasons the way she's plowing through oil!