If they had BPD (borderline personality disorder), in all likelihood they were not acting manipulative at all, and were just very often in distress and experiencing very strong, dysregulated feelings and emotions. BPD people being "manipulative" is a negative and inaccurate stigma, based on misunderstanding. It is also highly harmful, as people are told to always hold in their emotions, always be wary of trying to be "manipulative", or reveal their true feelings to anyone. Since Borderline people likely went through significant trauma in childhood, contributing to the disorder, they are being made to suffer a second round of emotional abuse and/or neglect due to ignorance and people not getting their facts straight.

People with NPD (narcissistic personality disorder), or ASPD (antisocial personality disorder) might exaggerate feelings to get attention or something else from you. Though if you were on a suicide hotline, ASPD people would have no reason for calling if not genuinely in distress, and i doubt you were encountering that many NPD people.

Is it that hard to believe that some people might actually be commonly dealing with very strong emotions and impulses they can't control? It's really unfair of you to label others emotions as fake and attention-seeking, when you really have very little data to go on as to whether that's the case or not.

And above all "Borderline people are not manipulative!" I wish i could shout that from the mountaintops, but i can't and most people don't care to listen anyways. You're inaccurately and likely prematurely applying the wrong label, and should give even regulars and even people you think you know well the benefit of the doubt.