I wouldn’t be surprised if most successful math majors scored lower than 31 on the ACT (or the equivalent on the SAT). Your daughter’s scores indicate that she could succeed in any major, as long as she was interested enough in the material to study and do the work. I’m a math major and some of the hardest classes I’ve taken were in computer science. This isn’t because computer science is innately harder than math, but because I practice math a lot more than I practice programming.