Is she correct /qa/? I think she might be bullshitting because

I think it's a metaphor for flat chests' superiority.

I can feel things that aren't "there" and so can you. It's called energy. Your image invokes the concept known as metaphysics, in this case an idealized body of energy present in the vessel powered by a spirit known as a human. It is not a metaphor for the heart, but in a way is a metaphor for what the heart produces: energy. Your brain produces some electricity, yes. But your heart produces much more. The hearts of children produce on average about a quarter of a volt, adults vary widely from .05 to half a volt. Those with severe depression can be in the range of the thousandths of a volt (.001). This is why many people experience a sort of energy shift as they leave childhood that leaves them off for the worst, as they have gone from a quarter of a volt to less while it appears certain others have become even more powerful from exiting childhood.
Of note: those that are super athletes can have hearts that generate an entire volt or more. My advice to anyone who is not physically active: Become physically active.