Should I pay mom's bills and get reimbursed?

If her income is from Social Security, they can assign you as 'Rep-payee'.
A checking account can be opened, entitled " daughter, as rep-payee for mother".

Look into it, because if she needs help, she may NEED a rep-payee, if not a POA.

Never co-mingle her funds with yours (or anyone else's for that matter). It is just not good accounting practice, imo.

Duplicate question see:
https://www.agingcare.com/questions/Ive-been-cashing-checks-for-mom-for-her-personal-spending-and-signing-the-backs-Am-that-going-to-loo-431988.htm?orderBy=recent&page=1#comment784321

Don't pay her bills out of your account. You'll eventually regret it.

This isn't a good idea. The problem is that each month it will look like she is giving your money and you will end up having to show what it was for if she ever applies for Medicaid or other assistance. Plus you could end up losing money if she doesn't reimburse you. What you can do is help your mother set up automatic payments from her own account. Another thing is that you could go to her house if possible and write the checks out and have her sign them. This is inconvenient, but Mother seems to have trust issues when it comes to her children. You'll have to work around that. The bad thing is that if she won't assign POA to anyone then ultimately someone may have to file for conservatorship if she becomes incapacitated. This is expensive and could be easily avoided by assigning a POA.