Flaubert uses Emma's desperate search for an almost unreal kind of romance as a conduit to infuse a language which is equally dissonant with reality. This occurs in chapter 12 during one of Emma's attempts to get Rodolphe to feel just as wildly needful of Emma as she is of him.
Oh no; no one else pleases you. There are some more beautiful, but I love you best. I know how to love best. I am your servant, your concubine! You are my king, my idol! You are good, you are beautiful, you are clever, you are strong!"
All of these words are all too familiar to Rodolphe, who compares Madame Bovary to all of his other mistresses. This would coincide with Flaubert's quote
Humanspeech is like a cracked tin kettle, on which we hammer out tunes to make bears dance when we long to move the stars.
While Emma intends for her words to assure Rodolphe's love for her (longing to move the stars) her words are actually falling on deaf ears. Rodolphe is tired of Emme's ridiculous words; his ego is certainly fed, but he can only react in a very limited way (we hammer out tunes to make bears dance).
Emma would repeat this behavior with Leon, whom she also loses even after the massive amounts of money she spends on him. Every time Emma tries to solidify her fantasies, she does it through exaggeration in language, behavior, and thought. Yet, all of these factors lead nowhere. Emma cannot satisfy the hunger she has for intense emotions. Even when she is in her dying bed her language is overly romantic, as if she were some heroine being sacrificed. Overall, it is true that language is like a cracked tin kettle: Emma did everything in her power to move away from her life and nothing actually happens.