If Mom is suffering from dementia her signature would be invalid.  Just fill out Form 2848 and attach your Durable POA (with Mom's signature) to it.

bwa--thank you. since I was planning on e-filing her returns is there a way to send a "scanned" POA attachement with the return? Also, is a 2848 needed for her Ohio State return? From your answer, it appears that a 8453 form is NOT necessary. Correct?
Thanks.

Unfortunately, Turbotax has no provision to include a scanned attachment of any sort that isn't a standard or required form.

You may have misunderstood my post - what I meant to say was "Just fill out Form 2848 and attach your Durable POA (with Mom's signature) to it", then send it in with Form 8453.

Most states accept IRS' POAs.  However, I'm not familiar enough with Ohio's procedures to tell you whether they do or not.

bwa----FYI----Ohio has it's own form for POA and does not recognize the IRS's form. The Ohio form is TBOR-1. Hope this helps if you ever get asked.

But if I want to e-file for my mom and I have power of attorney, what do I actually put on the signature line of her federal tax form? My name? Her name? Nothing?

I do not want to print the tax forms and mail them by post office - I want to e-file and pay what she owes on-line.

I understand that I need to fill out 2848 and 8453 and attach the POA and mail it in, but what do I actually sign the federal tax form with??

Sign the electronic return with your mother's name.  She is the taxpayer and the one submitting the return (with your help!).