What do I do? Need help please guys

Hi everyone. Kinda a long list sorry. I was best friends with my cousin (her name is Lucy) and there's only 18 days between us so naturally we were raised like sisters. Since year 8 this girl called grace came into the picture. I didn't mind at first I thought she was nice and didn't mind hanging out with her. Then slowly. Grace became one of mine and Lucy's best mates. It was like in mean girls, I was Karen, Lucy was Regina and grace was Gretchen but we are all nice people. And I didn't mind AT ALL because we all got along and were nice. Anyway, grace started to exclude me from stuff and would invite Lucy to stuff and not even tell me about it. For instance, a family barbecue, FAMILY barbecue and grace said that Lucy always comes to them so she doesn't have to be with her cousins. When I know that her cousins have come to see her and her family not Lucy. I don't get it. Anyway, so you get the idea. They exclude me without notice and just let me take it and in the past I've said stuff to them saying hey I don't like what your doing, but then they say oh sorry and do it again. Well today, I brought up on a chat group with them all in it, that I wanted to go job hunting over the summer and get a job and would anyone like to come with me? So grace bring up she wanted to get one next year and Lucy said the same. I didn't mind at first but then grace says TOGETHER? I wasn't happy. I couldn't believe it they literally just pushed out out completely. So I out a couple of GIFs and sad emojis and made it obvious I wasn't happy being left out. And she just brushed over it saying oh i thought it was only for this summer. I was like, when the hell did I say that. And so ye. Idk what to do or say coz they keep doing it. I think I want to start hanging out with the people from my primary school again coz I know that I'll have a place in their friend group. What are you thoughts pls lemme know 💖