Hi Travelling suse
Thanks for posting this introduction and welcome to bpdfamily
You believe your SIL might have BPD because she exhibits certain BPD traits. What BPD traits does she exhibit?
You also speak of her controlling behavior which sounds quite unpleasant indeed. Would you say that she uses things such as fear, obligation and guilt to try and intimidate and control others? We have an article here about this subject that you might find interesting, here's a short excerpt:
... .fear, obligation or guilt ("FOG" are the transactional dynamics at play between the controller and the person being controlled. Understanding these dynamics are useful to anyone trying to extricate themselves from the controlling behavior by another person and deal with their own compulsions to do things that are uncomfortable, undesirable, burdensome, or self-sacrificing for others.
You can read the entire article here:
Fear, Obligation and Guilt (FOG)You mention boundaries and I'm glad you did because they are very important when dealing with someone who has BPD. Being able to set and defend your boundaries is crucial for protecting and preserving your own well-being. To help you in this department I suggest you also take a look at another article and workshop we have here about boundaries:
Article: Getting Our Values and Boundaries in OrderWorkshop: Examples of boundariesHere's an excerpt from the article about boundaries which illustrates the link between boundaries and values:
Boundaries are how we define our values to others. A boundary is nothing more than the outer perimeters of our independent core values - it's like a fence - anything inside the boundary is consistent with our core values and anything outside the boundary is not. For example, if your independent core value is "always to be respectful of others" a boundary question might be "would abruptly walking out of the room when someone says something offensive be inside or outside of your definition of this value?" It's not always obvious as we all see things differently. As you can quickly see, with values, we have a significant responsibility to lead, educate and inform others - we must walk the walk, have effective communication and be consistent.
Take care and I hope you'll find these resources helpful