Hi, I suffer from all 3 conditions, similar to your girlfriend and I know my boyfriend has also been in a similar position as you. It's not a matter of doubting the love between the couple, because I truly believe that can be genuine, but I think it's more about understanding what works for that specific person. And sometimes that is tough too, because we ourselves don't really know what our specific triggers are and we are also processing and learning about ourselves as life progresses.
As someone who has experienced the other end of it from the point of being similar to your gf, I would say all I truly needed was to feel supported and less alone in the process because I, myself am still figuring myself out. And we do understand and sometimes even beat ourselves up for making our relationships feel harder to navigate, but reassuring us that we are in it together and being very mindful of how things are worded goes a long way (eg. raising the concern while also clarifying that you are not placing blame, but bringing up a concern that you wish to address together, emphasising the idea that its "us vs the problem" instead of "you vs me".
Ideally, if you're thinking of something more proactive, I reckon reading and understanding what each personality disorder entails and how that applies to your lives together could make a significant difference. Y'all can identify the potential conflicts y'all could foresee, and come up with a mutually beneficial plan to work on together. This comes in many forms but some tactics that helped me and my relationship were:
- Helping identify triggers and being very mindful of how conversations around those topics are bought up (for eg. providing reassurance that you are not validating any insecurities relating to that trigger) go a long way.
- Reassurance and support, whether it's via words or just simply asking if she needs help with something or just general acts of service; trust me, we notice.
- Coming up with logical solutions and breaking your exact feelings down (Eg. I feel this way because of for eg. this incident --> If we did (mutually beneficial solution) next time, maybe I won't feel this way). And it doesn't have to be much; it could just be a hug or an extra sentence to validate a feeling.
- Never blaming the other person for your feelings but more of accepting that this is how you feel and that you want to find a solution together (us vs the problem).
- Taking time to listen and understand both POVs. In any conflict, a normal initial response would be to get defensive. But stop for a while. Maybe have a safe word (mine with my bf is iced coffee haha) and take your own time to really understand how you felt and why, and then do the same about your partner's POV. When you are ready to come back to the convo with both POVs in mind, resume the convo then. (We may want to get it done with then and there, but I found out that I had to compromise with this so that we could understand each other better and not end up having repetitive arguments in between).
Obviously, no relationship is perfect, but we are working on ours every day, and these were some things I realised as we navigated it. And know you're not alone; both of you. There are many support groups and online resources that would help too, for both the person with BPD, ADHD, Autism, and their carer/partner as well. Genuinely hope the best for y'all and would love to help if there's any other way I can!