How do i get through to her?

I am in a fight with a friend... sort of. It all started with a text message. You see my 8th grade cl is going to Hershey for a trip. I wanted to room with two groups. I had a solution to our problem. Wednesday morning i sent the text saying my solution then Wednesday at lunch i decided to room with *A* *B* and *M*. A B and M didn't get the text until Thursday after i decided to room with them, Now A thinks i was lyeing about rooming with them when i wasn't. She is SUPER mad at me and won't listen to what i have to say. How do i get through to her?