I want to say a huge welcome to you and I can hear how scared and nervous you are about reaching out and writing your first post here, you are so very brave to get some support and some comfort, we are here for you, to talk and to help you through this really tough time. You will never be judged here and you can share as much or as little as you feel comfortable to..welcome Jayne20.
It is good that you have identified that the behaviours of others have made you feel so bad, I am so sorry this is happening to you, especially seeing that you felt like you had made some great friends. I probably don't need to say this, but real friends don't put their friends down, making up stories and generally making their friends feel very bad about themselves. It is so hurtful and so very unnecessary and it just does not need to happen. Their behavior says everything about them, this is not about you. You are so very wise to move away from this group of people, even if that means being by yourself until you find some new people to be friends with.
I feel like starting uni is somewhat similar to when one starts high school, the worry of finding new friends, the increased work load of school work, unfamiliar teachers, unfamiliar environment, it really is so much to get through, I think this is why sometimes people revert back to this immature behavior of "survival", that by making others feel bad it makes them feel good, when they too are probably struggling to adjust too. Does it make it right, absolutely not, but I feel like this is what might be driving this.
I am wondering how you are managing your anxiety and if you have been to have a chat with your GP? To get some medical advice and support at this time for you would be great. It is hard to speak up and I can see that you said this is the first time you have done this ..if you feel you cannot speak to a doctor you can write some points down and show them and they can start a conversation with you, also you could show them your post here as it does explain well how you are feeling.
I hear what you are saying in that the "happiest and bubbliest person in the room inside feels so very alone"...it really is a strange old thing anxiety, depression, mental illnesses, in that you can put on a big brave face and "appear" like everything is just peachy but inside it is a very different story, I am so proud of you for speaking up today.
Hope to chat to you some more.