Hi TDeer,
Welcome to our online family! You've come to the right place to find support for the challenge of dealing with your mil. There are many others here who will be able to relate very well and share their thoughts as to how they've dealt with similar situations.
I am very sorry that you have to deal with this at all. It is pure misery for you, I imagine. It sounds like she is being hurtful to you. How long has she been a part of your life? Does your husband see her behavior as being a problem at all?
Here is a link that may encourage you and help you to not feel so alone.
https://bpdfamily.com/content/Dr-Jekyll-and-Mr-Hyde BPDs are tough, as you well know. Please share as you can. You will not be condemned for sharing your thoughts here because we are on this journey together with you. Have you had time to read any of the information here at the site?
Wools