Come on Over for Dinner - S7-E23
Continuity mistake: Right after Carlos kills Alejandro with the candlestick, he throws the candlestick to the left of Alejandro's body. But a few seconds later the candlestick has suddenly moved to near Alejandro's head.
Answer: Kayla was sent away in episode 16 (The Gun Song) in season 4, after falsely accusing Lynette of child abuse. She now lives with her grandparents - probably Nora's parents.
I'm curious why we never see her again, why she never talked about, and why Tom never mentions visiting her.