I believe the meaning of this song goes along the lines of that the singer is already in a relationship with someone else, but they're having an affair with someone they have a hot/cold relationship with. And even though the person they're with may possibly love the singer, the singer knows she's using them and cheating on her other partner, thus making the metaphor that they've become the "other woman". (Even though we would think this would mean maybe the singer's second lover is a woman, the age-old metaphor is "I've become the other woman," not "I've become the other man," thus they could be either male or female.)
I believe the meaning of this song goes along the lines of that the singer is already in a relationship with someone else, but they're having an affair with someone they have a hot/cold relationship with. And even though the person they're with may possibly love the singer, the singer knows she's using them and cheating on her other partner, thus making the metaphor that they've become the "other woman". (Even though we would think this would mean maybe the singer's second lover is a woman, the age-old metaphor is "I've become the other woman," not "I've become the other man," thus they could be either male or female.)