I am Mom's POA. She more or less is using my house to threaten me cause she agreed to make the house payment. Any advice?

Without a lot of info to go by this is difficult to answer.
Does she need POA?
Are you a caregiver?
What is she threatening to do?

Undo the agreement. She has it in her mind that she now owns the house. If you need help, set up rent and get it in writing. Have her pay a set amount to help cover expenses.

Getting it in writing will protect you if Medicaid ever gets involved.

Need more info. I assume she lives there if she is making the payments. If not, that could cause problems down the line if she needs Medicaid.

What exactly is she threatening?

As long as mother is making your mortgage payment, she feels like she owns you which entitles her to say & do exactly what she wants, when she wants to.

Women of that generation seem excessively concerned with appearances, and keeping up with the Joneses. Why? Who knows. Probably because they're spoiled and entitled in general, I'd think, at least that's how it is with my 92 y/o mother. Dad treated her like a queen and let her get away with murder for the 68 years they were married. Now that he's gone, she feels like it's MY turn to be her 'yes man' which ain't happenin'.

Get her out of your house and take your life back, my friend. You can still be her POA with her living elsewhere.

Best of luck!