My 21F bestfriend has got a new friendship group she formed after meeting them abroad but now they are back and I 21F dont understand why I'm not included?

Me and my Best friend met on my first day of university and have lived together ever since. She has always had other friends outside of me like ones from her home town and her lectures etc. However she would always try to include me by inviting me out when she was with them. I am a bit shy and she is pretty social, I have adhd so struggle with friendships and have felt left out a lot throughout my life. But in our friendship It wasn't until recently that I felt left out and alone.

My friend went on a uni trip that i didn't go on and met a bunch of girls on it which she has now formed a friendship group. This was a very big trip abroad so I can understand that they formed a bond whilst there and i don't want to push in on their group. But it has been a while since this trip and as a group they always make plans and I feel like where I used to be invited with her other friends I am now excluded with this group. I dont think its intentional or cruel. The girls in it are all apart of my university & in the same city some of which I know decently well now and some I even knew before their trip so I just don't understand why I am left out. I have known one of the girls for the same amount of time I've known my friend and i used to go out with her and my friend occasionally but understood one on one friendship is important. But as they are now in a group and have known me for so long I feel left out. It would be okay if my friend spent a lot of time with me but I'm seeing less of her since she was in this group so thought becoming a part of it will solve this.

My best friend has now planned a trip with them and has planned other trips with all of her other (home) friends. But waited to make plans with me and now cant afford to have another vacation. I am supposed to be one of her best friends, yet i feel like i am always the last option. Especially having a disability I tend to feel as though I am not taken seriously and she would rather have more 'normal' friends. When i have hung out with the group its usually because I will question her about her plans and she kind of has the 'you can come if you want' attitude. The trip she is now going on with them is a place i was supposed to go months ago with my bf but it got cancelled and my friend knew this was somewhere I've always wanted to go. Now i have to sit in awkward situations when i am around her group hearing how excited they all are to go to this place. I confronted my friend about this specific trip and she even admitted it was awkward that they all were talking about it Infront of me.

I don't know if I'm toxic or overdramatic but I do feel like it wouldn't hurt if my friend included me more. Although i don't want to feel like a charity case. I do have other friends but she is my closest and her group is fun and i want to be apart of it. Any advice on if I'm valid in feeling this?

(*I am not solely reliant on this friendship and i dont know if explained it right in the description but I barely hang out with her anymore and she spends all of her time with them now whilst I'm sitting alone in the house we share when im not with my own friends and she doesn't tell me about any big plans she has until someone else brings it up so I am involved in barely anything she does)