This is such a great topic Mandy.  Perhaps "leading alone" is just another example of leading without a title and reinforces the notion that leadership is not about position.   Having people work for you does not make you a leader.  As you point out so eloquently, being a leader is about the choices we make.

I think anyone who chooses to lead in any given moment is alone though - the moment we speak up, step up or stand up for something we stand out. The people around us will follow our lead or they won't.  They may even try to knock us down overtly or covertly.

"Choosing to do, every day, that which is best for those you come into contact with through the course of your day." -- that is what leadership looks like in everyday action regardless of whether we run a company of 1 or 100,000.