Hi LaraK310,
Welcome to the BPD Family I'm on this board because my SO (significant other) has 2 daughters with an uBPDxw (undiagnosed BPD ex-wife) so I'm coming at things from a slightly different angle than you are.
I'm sorry to hear about the chaos that you are experiencing and totally agree that having someone with BPD in your life can be absolutely exhausting. No matter what role the person with BPD has in the family there are tools and strategies available that can help.
I'm curious what you see as the issues? I think us "steps" often have a lot of insight into the family dynamics of our partners because we come at things from an outside perspective. How do you and your husband approach parenting and discipline regarding DSD17 and the other kids for that matter? For example my SO and I talk things over but he is the parent that makes the ultimate decision and takes action regarding his kids and I do the same with mine. What is your husband's relationship with his daughter like? How would you define your role in the family? How old are the other kids in the family?
My first piece of advice is about self-care. You and your husband need to practice some self-care both individually and together if you are both exhausted, and feeling kind of disconnected from each other you can't be your best selves. It's like the oxygen mask demonstration on a plane you can't help anyone else unless you put your oxygen mask on first. Each of you need to make time to do something that you enjoy separately and together... .maybe you could each tag team so one of you gets a break and then the other gets a break. Maybe your husbands ex could help by having her daughter over for a day or over night so the two of you can have time alone together or with the other children. Talk with your husband and see if you can come up with a plan together.
You might consider therapy for you and your husband (this could fall under the self-care category), it could really help in terms of support for the two of you, it could help in terms of understanding your DSD17, and it could help in terms of tools to help you both. You might also recommend this site to your husband, it really helps to know you are not alone. My SO and I are both members here and it really helped us in terms of support, ideas, and tools. We learned to speak the same language and worked better as a team.
I'm going to share some links that might be helpful, some about validating DSD17 feelings (this is not about validating bad behavior but about validating DSD17 feelings behind the behavior so she feels heard). I'm also going to share some links about boundaries because they are huge when it comes to having someone with BPD in your life (pwBPD are excellent boundary busters so enforcing your boundaries is key). I'm also going to give you a link to the "Parenting a Child with BPD" board where you can engage with parents experiencing a similar situation.
ValidationIs listening with empathy to another's point of view, their feelings or their experience. It involves giving your full attention, and listening to both the feelings and the needs being expressed, and trying to understand by putting yourself in another's shoes.
https://bpdfamily.com/content/communication-skills-validationhttps://bpdfamily.com/content/communication-skills-dont-be-invalidatinghttps://bpdfamily.com/content/communication-skills-dont-be-invalidating;allhttps://bpdfamily.com/content/communication-skills-dont-be-invalidatingBoundariesAre when you put your values into action and clarify what is and what is not acceptable to you and act accordingly to defend these values.
https://bpdfamily.com/bpdresources/nk_a120.htmhttps://bpdfamily.com/message_board/index.php?topic=61684.0https://bpdfamily.com/content/values-and-boundarieshttps://bpdfamily.com/message_board/index.php?topic=167368.0Parenting Boardhttps://bpdfamily.com/message_board/index.php?board=4.0One final thing, read up on BPD if you haven't already, it's incredibly helpful to understand what BPD is. Two books that I particularly liked were... .
Stop Walking on Eggshells: Taking Your Life Back When Someone You Care About Has Borderline Personality Disorder by Randi Kreger
Overcoming Borderline Personality Disorder: A Family Guide for Healing and Changeby Valerie Porr M. A.
I'm so glad you've found us and hope I've provided some helpful information. I know other members will be along soon too with their comments and suggestions.
Hang in there
Panda39