Okay, I'm going to add my two-cents. Take it for what it's worth.
First, you are right. Your mother needs to be respected as both your mother and as a person created in God's image.
Second, you need to respect yourself, too. In this case, you need to insist that your mother treat you with the same respect that you should expect from any reasonable person.
How do you achieve these two things in your situation? Well, you turn the other cheek. A long time ago, someone explained to me that turning the other cheek, surrendering your cloak and going the extra mile does NOT mean rolling over and taking abuse. In its historical context, those illustrations highlighted the dignity of the sufferer. Back then, for example, you could slap someone with your palm in righteous indignation, but if you backhanded them across the other cheek, it was cruelty. You could take someone's tunic in court, but not his cloak; it's what he used as a blanket to keep his family warm at night. You could temporarily impress someone into service for one mile, but two was tantamount to slavery and illegal. Turning the other cheek and going the extra mile meant essentially exaggerating the other person's selfishness to the point that they realize what a jerk they have been, and doing so in a way that maintains your own dignity.
It's called establishing a boundary. You need to figure out what that looks like for you.
For me, it looks like this: "Sure, Mom, I'd be happy to help you out of yet another predictable financial mess. Just give me financial power of attorney."