One of my friends tried to kill them self. They were diagnosed with BPD. How can I be there for them?

Since BPD, otherwise known as Emotionally unstable personality disorder, is a hell of a personality disorder to live with because of the pervasive self-destruction and self-destructive impulses, identity instability, self-esteem fluctuation, emotional oversensitivity and abandonment fear and is also a very complex disorder and stigmatised disorder the best way you can be there for them is by educating yourself about the disorder and about the terms that are used when describing certain states of mind such as "dissociation" and "splitting" (and in rare cases even "psychosis") or terms describing relationships such as "favourite person". Participating in their therapeutic process. Having clear boundaries. Being gentle and mindful. Speaking in "we" terms - "We will get through this." Best video to look at would be dr. Fox's "How to manage the favourite person relationship". His whole channel is dedicated to managing life with personality disorders (specifically BPD) and she would benefit from his video/s just as much as you would. I wish you good luck! https://youtu.be/PB-rd8fMYdY