I think I want to major in either physics or bio…my guidance counselor recommends physics because she thinks that being a girl applying as a physics major will put me at an advantage. Is this true?
No, there are plenty of women in all STEM fields including Physics.
Read this. Hope this inspires you.
https://gizmodo.com/these-17-women-changed-the-face-of-physics-1689043918
Physics and bio are very different. You should choose what is more fun for you. That said, I agree with your counselor, if you do like physics and math over bio
One of my kids majored in physics and the other majored in biology. I think both would agree that a physics degree is more valuable in the job market.
If you have the profile of a serious physics student, it can help your application at some of the smaller, liberal arts schools that are otherwise over-run with humanities types and premeds. But very, very few students (male or female) actually do have this profile. The adcoms will probably see through an effort to disguise a future premed with a splash of ‘physics sauce’. On the other hand, if you have done your Regeneron Science Talent Search project in theoretical physics, then you can get past those suspicions and separate yourself from the rest of the applicants. I know because my D did have the profile of a serious physics student, and it absolutely helped her in the admissions process. But not everywhere.
For excellent undergraduate physics instruction for women, take a hard look at Bryn Mawr, Mt. Holyoke, and Smith. There is much to like at all three of those schools.