Sorry for your loss.
Thanks for the clarification, which while painful to pen, will help the others here give you some pointers.
My only concern is that where there is money and family etc there can be "issues", perceived or otherwise, and all I want to make sure is that you don't find yourself, through your helping your mother, on the wrong side of such issues.
Memories of what was verbally agreed at the time can very quickly fade through selective amnesia....