Hi,
To me it seems that in general you have a traumatic experience from the past with a situation of "losing a friend" and somehow I believe the behaviour of this girl even if you dont really know her is making you feel anxious that eventually will steal your friends.
First of all your friends are your friends and they are not an object that someone can steal from you like a pen or wallet. If your friends are trully *friends why would they leave you if you haven't done anything wrong to them? In general life goes fast and we might interact with certain people from time to time but your friend are always there no matter if you dont see them or dont talk to them for a while.
So please pass to this fear for your benefit and really make a list of who you really call "friend" and if they all fall in the same category.
Be confident that your happiness does not come from your friends but they can add to it. You should be able to feel happy without friends as wellI.
Nightmares can sometimes scare us but as soon as you stop thinking of them they will dissolve from your memory. Underneath of your anxious brain your mind plays games with nightmares and other kind of emotions; we humans some times dont understand.
If your nightmare comes again welcome it and let it go. Fall back to sleep and dont try to judge why or what happened and you had this nightmare.
And after all, the earth will always support you.
That's from me and I hope it helps.
