Buddy Sour? or just insecure?

So on sunday my best friend moved her new horse into the barn that I have had my horse at. We've only been there for like 2 months now and so my mare is still at the bottom of the herd. I expected her to be a jerk because when I moved her in all the horses that were at the bottom were jerks to her but they have sorta glommed on to each other. Her mare wont leave mines side no matter what. My mare could really care less. She gets a little distracted when we're riding but over all she is fine with it. The problem is my friends horse will run straight at us(and my friend refuses to believe me when I say she needs a harsher bit) and my friend cant get her to stop until she is right on top of us. again my mare doesn't care, but its really scary. Her horse is scared of just about everything and honestly seems to me like she is really insecure. She wont leave my mares side and when my friend introduces her to new things she is completely freaked and doesn't want to do anything but stand by my mare. Does this sound like buddy sourness to you or insecurity? I think she seems insecure but my friend refuses to believe it. Either way, how would you go about fixing it? thanks!