The text uses an idiom, an expression that cannot be understood literally.
The idiom speak of the devil suggests that Rachel had just been speaking about Felix. People say this when the person they've just been speaking about coincidentally arrives, as if summoned.
What does the idiom in this text suggest?
"Speak of the devil!" Rachel declared when Felix strolled into the room.
A: Rachel had just been speaking about Felix.
B: Rachel didn't trust Felix.