How can I protect myself from my mom's forgetfulness?

I agree with techie here. The bill paying will come up on her bank statement. It will show pretty much her monthly expenditures are the same. What I would worry about is the money given to your sister. Especially if its large amounts. If u ever need Medicaid, these large amounts will stick out. They could effect her receiving Medicaid. So for them, yes, I would make her sign something. If you reimburse yourself, have back up. I would take an envelope and keep receipts in it with the check # I used to reimburse myself. Moms been gonec2 yrs. Probate was closed last Sept. I still have them and will until the five yr anniversary of her death in case anyone comes back to me, like the IRS.😊

You might want to continue with the written direction for unusual disbursements, not for future justification to your mother but to other parties. At some point, it's possible a sibling or other family member will challenge your actions as POA and you may find yourself accounting for expenditures to a judge or a SW during Medicaid qualification. Document or journal everything as much as possible.

I do have a POA and I've been taking care of her finances.  I told the new doctor and she got soo upset with me and said why I keep telling everybody that she has dementia when she remembers things better I do. Her long memory is perfect but her short memory is very poor.  I stop going to her doctor with her just because she didn't want me to talk to the doctor. I arranged her home care person to take her now and asked the doctor office to put me as a primary contact if needed. I will try what you suggested. Thanks.

My mom would do that too, sign a written statement about something, then claim I forged it or that she had the right to change her mind. There is no reasoning with dementia. I doubt recording will work either. If you can just divert the conversation as quickly as possible, she might forget. Or say you'll get the money back. She might forget to bring it up again. So, if she does not yet admit to a poor memory, she might not want you to take over her finances and give you POA, right? Money issues, I think, are especially difficult for someone with dementia to deal with. They must feel really afraid when they don't understand what's going on with their money. What does the new doctor say about dementia?