In the poem, the image of the falling plums intersects with the image of a woman who is waiting for a man to come and to court her. Therefore, the first common ground to compare the fruit and a maiden is a similar period of life both are living at. For instance, the fact that the plums are falling hints on the fact that they are ripe or ready. Similarly, a maiden that contemplates them falling has reached a particular age and is talking about finding a couple and the future marriage. In other words, she is ripe as a fruit.
Apart from that, both a fruit and a woman are staying at the threshold of a new life. A falling plum is leaving a place of living, the one it has been in since birth. Breaking with the roots and chains that kept this fruit tied to one place can be interpreted as the fact of leaving a home of parents and moving into another place – the home of a husband. Subsequently, both plum and a maiden are going to enter the new stage of life.
In addition, in my opinion, the ripe and falling plums, which are to be gathered by someone, represent a traditional passiveness of a woman when it comes to the issue of marriage. The following is reinforced by the language used, which is in a passive voice. A woman waits until someone will court her, but does not court herself. Similarly, a fruit grows, becomes ripe and further he is either gathered by someone or not.