If Celia is associated with water and all that it symbolizes, Felicia embodies fire. We hate to get all obvious on you, but just in case you missed it: Felicia exacts revenge on her husband Hugo by setting his head on fire. She is burning with illness and resentment and needs to rid herself of the conflagration before it consumes her. She, like her mother, also burns with the "fire" of erotic love but doesn't have the internal resources to deal, as Celia does.
The element of fire symbolizes some fairly unsavory realities in Felicia's life. When she is pregnant with Ivanito, she's nauseous and miserable, but also infected in her private bits with the syphilis her husband brought back from Morocco. If you've spent any time with the sonnets of Shakespeare, you'll know that he uses fire to speak figuratively about this disease (check out Sonnet 154) and that early treatments for it required superheated baths and sweatboxes.
Also, any kind of neurological disorder is often referred to as a "fire in the brain," whether it's something like encephalitis or depression. It's quite possible that these two figurative ways of speaking about illness meet up in Felicia: we know that she suffers from both sexually transmitted disease and from mental illness. We're sorry to be the ones to make these connections for you, but there it is.
On a completely different note, there's the matter of the combustible santera. Celia brings the woman who originally told her she had a "wet landscape" in her palm back to her house in Santa Teresa del Mar to help her heal Javier and "she trembles once, twice, and slides against Celia in a heap on the sidewalk, smoking like a wet fire, sweet and musky, until nothing is left of her but her fringed cotton shawl" ("Baskets," 160). Despite Celia's balancing element of water, she is unable to quench the fire that begins to consume them all.