In the first verse speaker is young and immature, wanting nothing more than to get attention from her big sister, but at the same time she resents her deeply for having such a great life.
The second stanza shows the big sister showing more love to the speaker, which makes her very happy.
In the next verse, the little sister tries to become as naturally perfect as her sister, to no avail.
In the last lines, several years later, the sister is late, and in her mourning the grown-up speaker thinks about all that could have been, and how their relationship would have further blossomed.
What I get from it...
In the first verse speaker is young and immature, wanting nothing more than to get attention from her big sister, but at the same time she resents her deeply for having such a great life.
The second stanza shows the big sister showing more love to the speaker, which makes her very happy.
In the next verse, the little sister tries to become as naturally perfect as her sister, to no avail.
In the last lines, several years later, the sister is late, and in her mourning the grown-up speaker thinks about all that could have been, and how their relationship would have further blossomed.