Answer:
Phoebe Caulfield is real (I assume by real/fake, you mean phony or not)
Step-by-step explanation:
Of all the characters in the book, Holden has the closest connection with Phoebe, he constantly "kills" him. Phoebe is one of the characters who can fully through Holden's lies. She often says what is on her mind, without worrying about offending Holden. She is not at all phony, at least in Holden's eyes.