I feel that the theme of the story is that love is blind and fragile. The female speaker in the story talks about how she wishes she had someone that truly loved her and appreciates every little detail of her. She broke up with her boyfriend Mike the day after Valentines day to be with the male speaker in the story because she saw the card that he had wrote for his girlfriend Jenny and immediately knew then that she wanted to be with someone like him. She was touched by the card and the feelings that he expressed for Jenny. When the male speaker and his girlfriend Jenny broke up she stepped in and got with him. When the female speaker in the story tells the male speaker why she fell in love with him he tells her that he wasn't the one who wrote that card and that it was actually Mike. In the story it says "A single tear crawled down her cheek". The female speaker realized that she broke up with the person that she truly wanted to be with. She wanted to be with the person who wrote the card which she thought was the male speaker in the story but it was actually Mike who she broke up with. The theme that love is blind is evident here.
The diminishing candle flame in the story is a symbol for the relationship of the speaker's in the story. The candle flame is burning out and so is their relationship. In the quote "A single tear crawled down her cheek as the flame died leaving only a trail of smoke and the smell soot." she is realizing that the relationship is over just as the candle flame burns out. When the flame goes out so does the relationship.
http://www.shortbreadstories.co.uk/story/view/the_flame/