Why does Priscilla reject Miles Standish?

"The Courtship of Miles Standish" is a narrative poem written by Henry Wadsworth Longfellow in the year 1858. It is set in the time of early colonists of North America and in an environment of conflict between Native Americans and the pilgrims who settled in Plymouth. Additionally, the story is centered on a love triangle.
Miles Standish, our titular character, and his friend John Alden are both in love with a "Puritan maiden" named Priscilla. In fact, in the beginning, Miles is unaware that John also loves Priscilla, and he asks John to propose to Priscilla on his behalf. Priscilla tells John that because Miles did not make the proposal himself and has never before shown Priscilla that he loves her, she will not marry him. In her own words:

If the great Captain of Plymouth is so very eager to wed me,
Why does he not come himself, and take the trouble to woo me?
If I am not worth the wooing, I surely am not worth the winning!

Additionally, she later says:


This is not right nor just: for surely a woman's affection
Is not a thing to be asked for, and had for only the asking.
When one is truly in love, one not only says it, but shows it.
Had he but waited awhile, had he only showed that he loved me,
Even this Captain of yours — who knows? — at last might have won me,
Old and rough as he is; but now it never can happen.

However, it is pretty clear that Priscilla's main reason for rejecting Miles is that she would rather receive a proposal from John, especially shown when she asks "Why don’t you speak for yourself, John?"