Themes explored in this poem include female rivalry, the difficulty of sustaining romantic relationships and the way that the past can intrude on and disrupt present happiness.
The mother in the poem clearly looks down upon the girlfriend. Despite the invitation she has received to stay in her home, the mother treats her with sarcasm and contempt. She doesn't regard her as a permanent addition to her son's life and makes sure that the young woman is aware that she is only passing through as others have before. The mother is particularly keen to remind her of her own greater importance in her son's life.
At first the younger woman is sure of her ability to defeat her rival for the affection of her son and to establish her place in his life for their future together. However, by stanza two she starts to lose confidence in her relationship. Seeing the childhood things that fill her boyfriend's old room and how lovingly they have been preserved by his mother, she starts to question whether her own more recent arrival in his life can possibly last.
There is the idea that it is by confronting information about her boyfriend's previous life which makes the young woman question their relationship. Is she with the right person for her to build a life with? She wonders about his previous relationships and whether his lack of commitment to starting a family together means that they will never be able to establish a permanent connection.