How to handle this situation with foster sister

[EustaciaVye01]

My foster sister is in her 20's. She has moved out from my parents house. I am in my late 30's.
My foster sister will be graduating this year and she is upset because we haven't booked a holiday for her to celebrate her graduation. I didn't even know that this was a thing? My parents and I were going to take her out for dinner and give her a nice present.

Backstory- she has fallen out majorly with my sister. (I only have 1 biological sibling).

Every year we take a family holiday. Last summer I couldn't go because my husband's niece was getting married during that time.

My foster sister doesn't want to go on the holiday with my sister but she feels left out and gets very angry with the rest of us. My sister is the main person who books and organises the holiday. My parents are elderly.

Anyway so for Summer 2025, my sister has booked a holiday for my parents, her kids and for my family.
My foster sister is feeling left out. (I have tried many times to mediate but it ends in a huge slanging match and I don't have the energy for it)

My foster sister rang me- shouting and swearing that we shouldn't go on holiday when she is graduating. I don't know what to do....

If you got this far- thank you for reading.

Perhaps you've taken on the role of fixer OP. It's not your place to fix anything. Your FS and S need to work things out if they can, sadly it might be they don't. You just look after yourself in all this

I absolutely hate family holidays- either with my family because of my original post or with my inlaws.
I was only doing this for my parents who wanted a holiday with their grandchildren. I've spoken to Mum and she is fed up of it all too. No more family holidays for us..

She was given Camhs appointments which are like gold dust but she refused to go. You can't make her do anything. She was excluded from school at 14 for her behaviour.

@EmberAsh @FabulousPharmacyst @StrongasSixpence thank you or your kind messages.

Honestly, I feel awful saying this but I wish my mum didn't foster her. Our lives have been turned upside down and I haven't got anything left to give to her.
I'm retraining in a new field, I have 4 children of my own and I'm exhausted by the drama.

She is screaming at my mum to change the holiday- ie take her and not my sister and her kids....I told mum to just put the phone down and speak to her when she is calm.

Yes

This forum is full of threads of people going NC over behaviour. Your faster sister is not acting in a good way and is not getting the help she no doubt needs.
You can't fix other people. You can only ajust your response