I'm with those who say work to keep her exposed to a lot of subjects and keep the options open. Perhaps helping her explore the future majors/opportunities that have social aspects (teamwork, problem-solving, etc.), rely upon good writing and yet reward math talent/knowledge. I'm thinking big consulting firms at the moment, but there are plenty of other options.
Personally, I wish someone had encouraged/supported me more in math so those options had remained open for me. I was not as good in it as I was at writing, but was far above average, right up to the point where it became tedious and my love of chitchatting in class/daydreaming took over. I wound up in my major because I had very strong writing/verbal skills. It was a skill set that served me well for many years, but turned out not to be a passion.
