I have a friend who I met a couple of years ago, who has become seriously territorial with friendships with other people. I have a friend I have known for years, and if we do anything together, shopping, even a quick coffee, without inviting her, newer-friend is LIVID, never confronts us, but is icily polite and fumes when we see her so it becomes awkward. Newer-friend has LOTS of other friends, sometimes we go out with her and them too, often she meets them without inviting me and old-friend, which is obviously fine - I understand people have lots of friends and can't do everything together! But she doesn't seem to understand this applies to her too.
It's making things very awkward, because this territorial behaviour makes you want to invite her to coffee/shopping/anything even less!
Any one else had territorial friend trouble with an adult?! It's exhausting, and feel too old for this.