I think trigger can mean different things to different people, which is why I'm not a fan of the word because it's so non-specific; it can be something or someone or a situation that makes you sad, or annoyed, or angry, or lowers your self esteem, etc. I don't think all 'triggers' result in BP episodes. They can, perhaps more frequently, be interpersonal in nature and lead to the feelings above, including SI.

I think therapy can potentially help us notice when these situations arise and teach us how to deal with them. Good luck on your journey!