Can three sisters share power of attorney even though the mother now lives with the elder sister?

Sounds like she is too far gone to sign another POA. Any changes now would have to be done via guardianship hearing. See an attorney.

Splitting the duties of POA among siblings is never a good idea. If you do a search here under "POA" you'll come across numerous stories about siblings sharing POA and how it's close to impossible to make it work.

Some people with POA go on a power trip. Others dig in their heels and demand that things be done their way. There can be control issues, a lack of wanting to compromise. The problems are endless.

There should be only one POA and if the other siblings feel left out then the POA can delegate tasks to the other siblings if the POA wishes. As the eldest sibling I was POA for both my mom and dad but I called upon my brother's assistance and we split the duties. I took care of everything medical and he took care of everything business. It worked out very well and my brother was a tremendous help.

I hope you will think very carefully before taking this step and consider only 1 person for POA.

Ever hear the saying "Too many chefs in the kitchen spoils the soup"? That definitely applies to multiple POA's. Getting three individuals to coordinate and agree on things will be a nightmare- especially as your mothers condition worsens.

Come up with ONE person to be POA with others as contingent. Three people trying to coordinate all care issues is almost impossible.