My dad is still capable of handling the finances, but not when it comes to medical care and getting answers for mom. How do I become legally responsible?

She gave me copies of her and dad's living will years ago so I have that. Mom is currently in skilled care for rehab and has had two trips to the hospital while there. One for a fall and one for vomiting coffee grounds/blood. The Dr. wasn't there when I was and I'd like to be able to contact him and speak to him....I guess I'll have to find out when her next appointment is and be there.

I'll take that next step and make sure I get notified. Thank you for responding!

If Dad is still handling all the finances, then all you really need is to accompany Mom to her doctor appointments and have her give them permission to give you information and to notify you of her appointments and care, etc. No legal documents needed for that. Next, you can have her execute a Power of Attorney and a Health Care Directive (also known as a Living Will). EVERYONE should have these done, regardless of their age or health. They do not take any control away from her, but will allow you to step in when it does become necessary. And it will save you from having to rush around in crisis mode if something unforseen were to happen.