Hello Etdja and welcome to the Parenting Board.
I'm so glad that you are here looking for help and answers regarding your d8.
My daughter was dx w/ODD at age 11 and then emerging BPD at age 12. We were fortunate to get a diagnoses so early in her life as it led our family to the understanding and skill sets needed to get her the help we all needed. BPD is a family disorder as it affects all the relationships within the family so we each needed to change the way we interacted with ourselves and each other.
I, nor anyone else here can diagnose your daughter. What we can do is give you the support you need as a parent to a sensitive child and help you learn the skills that help you parent her. One of the best resources I came across for parenting a young, sensitive child is the book
Parenting a Child with Intense Emotions by Pat Harvey and Janine Penzo. It teaches DBT skills to mirror for our kids and these same skills help us as parents be calm in the face of a storm of emotions. I hope that you will click on the link I provide here and take a look at the reviews we have and explore the book.
I look forward to learning more about your daughter and your family so that I can be an ongoing source of support for you.
lbj