I'd recommend taking courses in CS that will cover material she won't come across in math classes. So I'd say compilers and operating systems. Game theory and

I'd recommend taking courses in CS that will cover material she won't come across in math classes. So I'd say compilers and operating systems. Game theory and AI? Sure, but I don't think a math major would have much trouble reading in those areas on her own. Whereas something grounded in compilers or OS would elude her unless she had a background in these areas.