In interviews, Tanita has been rather modest about her intentions behind the song Leaving the Party, offering a fairly literal interpretation of the lyrics. I am more inclined to dwell on the more figurative elements of the song, as opposed to a strict view of the song's narrator as little more than a wallflower. The line "I'm not here to enjoy you / I am here to endure you" (especially when sung with that wonderful strain mentioned in DeeDee's post) is a fantastic statement of purpose that easily transcends the literal surroundings of the party in the lyric. Tanita has mentioned that she was striving for a "cheesy" effect with the strings and horns in the song, which provide a comical subtext to, and commentary on, the drama that unfolds in the song.
If I remember her comments in articles correctly, Tanita was offered a four-album deal from Warner's after the success of Ancient Heart, a deal that was more common at the time than it is now. As she was recording Lovers in the City, she was not given any indication from the company that she would be re-signed (probably they were waiting to see how well Lovers performed). Comments made during the promotion of The Cappuccino Songs suggest that Tanita was sufficiently unhappy with Warner's to lend the conscious intent suggested by Graham to the song Leaving the Party. Certainly there was no love lost between Tanita and Warner's.