The music mogul has reportedly ordered the 27-year-old singer - who is a judge on his UK TV show `The X Factor` - to curb her rumoured romance with dancer Derek Hough in order to concentrate on getting back to full health after recently been stricken with potentially-fatal malaria.
A source told Reveal magazine: "Simon has had serious words with Cheryl and gave her a list of things she needs to sort out.
"He`s demanded that she puts her love life on hold - he feels Derek is a distraction that she simply doesn`t need. Derek is always hanging around on set with her and Cheryl is constantly trying to keep him happy."
The 50-year-old star is also said to be planning to find a lifestyle coach to help the `Fight for This Love` singer - who split from soccer star husband Ashley Cole in February following allegations he had been unfaithful - juggle her hectic schedule.
The source added: "SimonwantsCheryl to accept more help, rather than try and battle on by herself.
"He told her everyone in the US has a lifestyle guru and that he will get someone to work with her.
"Cheryl hates the idea because she is a very private person, but Simon is insisting on it. He believes having someone with her is the only way to guarantee she will eat, sleep and talk about her problems."