My sister is 16, 17 in about five months. 
My sister has intense abandonment issues, I think it stems from my family and their constant arguing (parents). 
My parents have gotten better now, but obviously you can’t reverse trauma. 
I recently got diagnosed with OCD (finally) and it made me realize as to why I have so much relationship issues (retroactive jealousy and rocd), but my sister hasn’t been diagnosed with anything. 
Although I did just have her begin therapy. I think she needs it. I think everyone does tbh. But because she’s underage, she can’t really talk about emotional abuse, etc, which makes sense as therapists are mandated reporters. 
Anyway- every time my sister and I argue, well, not every time, but more often than not, she begins crying. She doesn’t really manipulate me or anything (and I’m saying this not in a malicious way), but she does cry and get angry. 
I don’t know if it has to do with her being a teenager and having emotional instability as all teens do, or if it’s something more worrisome. 
I love my sister
She also suffers from body dysmorphia. 
I’ve asked her what she wants to be and she’s gone from saying a lawyer to idk, maybe sociology. Is that enough to rule in identity confusion, or no? 
I don’t have much knowledge of BPD, I just have some due to all the psych classes I’ve taken, but I can’t help but worry about her well being sometimes. I love her so much but sometimes i don’t want to talk about the latest argument my parents had with her. 
Her identity has become my parents arguments. 
I want her to set goals for herself, what does she want to grow in, what interests her, etc. 
everything is also harder for teenagers right now too. 
They’re inside all the time. 
School is online, everyday, and she’s also stressed from homework and exams. 
I don’t know man, 
Even if she does have BPD, it doesn’t seem like it’s that bad. 
Does it look different in teens to begin with?