Why would someone do this?

I was on Vaca with 3 girls. Two were close friends of mine while the other I just met. She was very sweet in the group chat before we all met in person. As soon as she met me she completely changed behavior. When she took pictures she never offered to take a group picture/excluded me out of the frame or she would ask me to take some photos of them with her camera. Or would not completely include me in conversations/talk about people I did not know. As soon as we parted ways after the trip she removed me from social media but not the other girl. I really was left hurt and confused by her behavior as I was nothing but nice to her.