Do your friends/SOs have friends?

I'm glad someone brought up this topic. i had this problem a few weeks ago. I am in a new country and here i mostly have one close friend, we are really close and both have mental health problems. She has a few other close friends though and i kind of accepted that fact at first but some time ago i started to feel jealous, needy and insecure, especially when she went away on holiday with a girl that she became close to. i felt like losing her, not because she meant it but because i assumed that anyone else was much more attractive/interesting/fun/supporting to be with so it's natural that when she makes more friends, she will leave me out. somehow i managed to talk to her about it at some point and was reassured that it wouldn't happen, that i can talk when i feel needy and insecure because she understands it and it made me feel much much better. I still have lots of issues but opening up to her and saying what i felt made it all so much better - not only because i feel more secure in our friendship, but also because for the first time i had the courage to talk honestly and it gave me a lot of confidence. I'm learning to be more open and to trust more that people won't leave me.