Your four-year-old actually needs to talk a lot. Though she's become much more fluent in her use of language, your preschooler is still practicing with different sounds and words. During this year, she'll probably love words that exaggerate: enormous, tremendous, and emergency, for example.
Your child also will begin to pick up slang this year, including some "swear words" and mild "bathroom humor." Try not to appear shocked or scold or punish your child when she uses these words. Keep in mind that your preschooler is merely fooling around with vocal sounds and new language. If you ignore—or at least avoid overreacting—to her experiments with "impolite" words, she will probably lose interest in them after a while. (Of course, other children may reinforce her use of these words through their reactions.)
Your four-year-old may begin to love wordplay of all kinds. Of course, she's loved silly sounding words and made-up words for more than a year now. But now she will begin to laugh at puns and riddles (sometimes whether she gets the joke or not). She will play with rhyming words. She may even begin to appreciate the more sophisticated wordplay of Spoonerisms, in which you exchange the initial sounds of two adjacent words (for example, "brazen red" for "raisin bread"). Encourage your child to play with nonsense words and chants. If she can have fun with words, it will help build a love of language.
Besides playing with words, your preschooler may begin to use them to talk about increasingly abstract ideas. Your child may, for instance, explore aloud her ideas about God, about love in general, about truth, about death, and so on. If she does, your four-year-old will want—and deserve—to be taken seriously.
Try to avoid laughing at her ideas or the way she expresses them. Don't be embarrassed if she says something in public you'd never say. And avoid quoting your child in a patronizing or even amused way within her earshot. (Of course, you will want to share some of these treasures—but be sensitive to your child's feelings.) Though her ideas—or the funny way she says them—may be amusing to you, your child is probably dead serious. So try to respond in kind—or you may inhibit her from speaking her mind and sharing her thoughts in the future.