My friend unloaded on me that her friend has BPD and is suicidal. 

I'll call my friend Sarah and her friend josh. 

Josh and Sarah are not dating, they are strictly friends. Josh has been requesting that Sarah update him on where she is and who she's with at all times. Apparently it freaks him out when he doesnt know where she is at all times. She does what he says because he's suicidal and she doesn't want anything to happen to him.

Is this related to BPD in any way??