Pay Deceased Credit Card from Her Own Account

My question involves estate proceedings in the state of: California.

I was handling my late mom's accounts and bills in the final months
before her death. She has a pour-over will, and a now irrevocable trust.
The checking account is listed as an asset in her trust. I will be her
executor and trustee. I have access to all of her checking and credit card
accounts online. Not sure if it matters, but there are two beneficiaries of
the trust, and I am one of them. Both the checking and credit card accounts
are in my mother's name.

Can I just call the credit card company and have them take the money
they are owed out of mom's checking account? That's what I was doing
when she was still alive.

Or is this going to be way more complicated than that, since she is now
passed away.

A related question is that my nephew was helping me provide 24x7 home
care for a fee my mom offered to him in the final weeks of her life. A
few days after my mom passed, I did a bill-pay to him for his final payment
from my mom's account.

I later found, on this site, that doing so might have been a felony. The check
is still in processing, but too late to cancel. My nephew has agreed to tear it
up and I will make him whole with a check from my own account, which I plan
on accounting for as a loan to the trust. So the check from my mom's account
will never actually get cashed. Have I narrowly avoided committing a felony,
or should I still be worried about something? The amount was small; $300.

Pay Deceased Credit Card from Her Own Account