☆.A.
You have the right to feel whatever you feel about Sandra.
But friends don't come with strings attached.
You would include the hostess friend forever? For a week? A year?
I've met some great women through other friends, and guess what? What I have now with those women IS a friendship. The original friend doesn't need to be included in everything we do, every conversation, etc.
I think if you say something, then you can kiss all of those friendships goodbye. Maybe they are true, great friends, maybe they're not--I don't know. I don't know them. You do!
Good luck!