Welcome Baronesa: I'm so sorry about your daughter's problems and the difficulty she is having.
I had to call the police maybe twice because she's so aggressive, they took her to a hospital, they talked to her and the doctors and nurses said that she was such a nice person and her aggressiveness was because the pot and was behavioral problems.
Did they do a drug test, when she went to the hospital? Just wondering if she could have had something in her system, in addition to pot. Has she had any therapy?
She is less aggressive now but her mood can change very fast. One day she hates the next day she loves me. She still using pot and has been consistent with her job. But unfortunately she quit school again because she was to stressed out with test and homework. My husband and I are trying to learn as much as possible about the disorder so we can help her.
Does your daughter accept that she has BPD and needs help to manage it? It will help her to learn some healthy ways to self-soothe and manage her emotions.
Have you asked her about the pot?  :)oes it help soothe her on some occasions and then agitate her at times? I'm not a pot user, but I understand that there are different strains of pot and that some strains are more suited for certain problems.
The link below leads to a section, with a lot of helpful information for parents.
Lessons: What Can a Parent Do?