Hi SpottedDog,
And

Welcome to this board!
It can be so confusing and frightening to deal with this illness.
You are in the right place, there is a number of step-moms here. Each of us has a different situation, yet there are so many similarities!
You can find support on this board and also some very useful tools and information that helps coping with this difficult illness... .
This might be a good place to start:
https://bpdfamily.com/message_board/index.php?topic=114267.0;wap2I am in the step-mom relationship to my grown step-daughter with BPD. And as I find from our situation and that of some others, it is not uncommon to have a difficulty making a connection with our step-child who has BPD. And you are right - we have even less control over the situation than their natural parents. Which is frustrating in and of itself.
I personally find my place to fit in, in trying to create peace and structure (mainly through boundaries and validation), and provide support for my other family members who are all affected by our daughter's behaviors, while trying to include her. I do my best to learn as much as I can about this illness and help support my husband in his dealing with her (he appreciates my input as I am better able to see things objectively).
It could put a strain on our marital relationship if we did not invest enough time in trying to understand and validate each others' experience and work through the issues with our daughter/step-daughter.
Maybe in the future, as time goes on, and I am able to apply more of the new skills, I hope to be able to make a new, real connection with my step-daughter. But it will also depend on her, so I am open to it, but I do not dwell on it for now. I had to go through my own process of grieving the r/s that I hoped for with her, and that is sufficient for now... .
You are still in the tender years of forging your new blended family. Times like these are always trying for all of the family members involved. One with a possible emerging BPD can both: have an extremely hard time adjusting AND create a lot of additional stress.
Sending you a as you are in a difficult spot.
Welcome again, looking forward to reading your posts, SpottedDog