in thinking my friend is unreasonable?

[Misskittykat]

I have 2 good friends who know eachother but are not close like I am with them both.I think its ok to do things with 1 of them and not invite the other but when I went away for the weekend recently with friend A friend B got stroppy and implied that I was wrong not to invite her yet its ok for her to do things without me being invited and Im fine with that! Im nearly 40 I feel like im too old for this! What do you think?

You're right, anyone over 16 is way too old for this. If Friend B has a problem then it is HER problem not yours.
Stick to your guns or she will continue to try and make you feel bad about not involving her in every aspect of your life

I think maybe its because Im her best friend and as my circle of friends is quite small I dont usually do a lot of things without including her, but she does and Im not bothered at all!

No YANBU it's good to see people on their own sometimes and even if all 3 of you get on well together there will be things you have in common with friend A but not friend B and vice versa
My sister has two close friends who are both close friends with eachother but they never do anything all 3 of them - it is just the way that friendship works

thank you

Maybe she's jealous or lonely. YANBU but maybe there's a reason for her bad behavior.