Symbolism, Imagery, Allegory
Fear the Fire
After Kempe spiritually "marries" God the Father, she's given several tokens as a mark of favor—wedding presents, if you will. The most significant of these is the fire of love in her heart, which Kempe describes in this way:
Our Lord also gave her another token which lasted about sixteen years, and increased ever more and more, and that was a flame of fire of love—marvellously hot and delectable and very comforting, never diminishing but ever increasing [...]. (I.35.124-125)
Kempe also wants us to understand that while this "flame" is certainly mystical, it's also very real to her, and she feels it "as veritably as a man would feel the material fire if he put his hand or finger into it" (I.35.125). As you can imagine, this freaks her out pretty well at first, until Jesus explains things to her: "[...] this heat is the heat of the Holy Ghost [...] and you know very well that wherever the Holy Ghost is, there is the Father, and where the Father is, there is the Son [...]" (I.35.125).
Burning for You
Jesus's words are all very comforting, except that the fire of love causes Kempe to act in bizarre ways, which isolates her from the rest of the world. Because it is a hybrid mystical/physical feeling, Kempe often becomes overwhelmed by these sensations. In fact, this "fire" makes her behave like a drunk, "turn[ing] herself first on one side and then on the other, with great weeping and sobbing [...]" (I.41.135) or "reeling about on all sides [...] for the fervour of love and devotion that God put into her soul" (I.82.239).
Kempe can hardly help her responses when she's "all enflamed with the fire of love," but it doesn't make things easy for her. And while the fire is a token of love, it's a kind of love that wounds with its violence and leaves Kempe at the mercy of those who think she's crackers.
It makes it even more difficult for Kempe's priest-scribe-friend to support her in the face of criticism—that is, until he reads about Richard Rolle's perfectly named Incendium Amoris (that's Fire of Love to us). Once he realizes that a bona fide male mystic has experienced the same thing, it "prompted him to give credence to the said creature" (I.62.193). Problem solved. At least on that front.