So years ago, my ex and i were dating for a few while. Until one day he introduced me to his "bff/sister" of a childhood friend who had diagnosed BPD . I thought hey this is good and all until one time when we were at a gathering, she decided to wear his clothes(not hand me downs, like actually his clothes) in front of me for no reason at all. I found it really really odd , so i decided to bring this up to my ex and my other friends. They all thought its normal.

So heres the list of other things the "sister" did which i found odd but to the rest are normal:
-sending nudes to everyone including my ex(despite that they call each other brother/sister)
-always calling everyone ESPECIALLY my ex when she attempted suicide (and the dates of her attempts are always coincide with the times me and my ex were on a date, like less than a week later)
-talking to my ex EVERY single day regardless of knowing that my ex and i were together
-shaming/talking bad about my ex behind her back (yet my ex finds her extremely friendly and caring)
-accusing me of being a mean and judgemental person in front of everyone just bcos i was questiong her odd behaviour towards me and my ex, i mean no disrespect tho (but this accusation is all in the form of sweet talk she usually does in front of everyone including men)
-doesnt like sharing her friends with mine, but making sure my friends woould be close to her more than to me

I just wanna ask to everyone especially to the ones diagnosed BPD, are all of this behaviour considered as impulsive typical/justified BPD behaviour or is she being a jerk in general?

I mean no disrespect to the ones with mental illness i am simply curious