Public Health/biology double major is going to be intense (of course some may not find it to be). Public Health is a highly competitive admit at some schools. Biostats is a good major, and falls within public health.
Does she enjoy foreign languages? Would she consider a Spanish minor? Public Health + Spanish is a nice combination, but she will also need whatever premed classes are not included in the major.
A public health major with research experience will also set her up for a career, but all of the public health majors I know eventually went to grad school (and are employed).