I have a knot in my stomach over this..?

There's a chance that Samantha may be jealous of your friendship with Leila. If anything, you should talk to Samanth about and this and be honest with her. If it's really bothering you and you feel that she won't listen, then maybe it's time to take a step back and maybe find new friends, until things cool down. You could also try talking to Leila and tell her what's been going on. I really hope everything works out! Best of luck! :)