[Dottore]

If your mother is 89, it is urgent that you begin this dialogue with your siblings - and with her. Do not put this off.

You need to get a complete picture of your mothers finances while she is of sound mind. That option could be gone over night.

You need to get a clear picture of what is doable with her money. You need to have a game plan. And if her money is not enough, you need to have a clear understanding
with your siblings about the shortfall.

You need plans and backup plans. Study all the options. Get all the information now. These things always sneak up on you, and then you will not have the time to go through these things as carefully as you do now.

Oh yes, and find out where everything is. (addresses, accounts, passwords, valuables, papers etc etc.)