Welcome HerDaughter: I'm sorry about your situation with your mom. It can be a challenge to set boundaries, and Fear, Obligation and Guilt (FOG) is common. Your mom can make a choice to get treatment. If she fails to do that, then she is responsible for a very quiet Christmas - not you. Sometimes, the road to sanity is to stay firm with a boundary.
The links below can be helpful: (Click on the green words)FOG BOUNDARIESAre you able to share some details about our mom's behaviors? Does she have an issue with depression and/or anxiety, along with BPD?
There are several links to more helpful information, to the upper right of this post. Have you read any books on BPD?