has praised Derek Hough for saving her life.
The Girls Aloud
star - who is on the mend after falling ill with malaria - has thanked her close friend for demanding medics carried out further tests when her condition was still undiagnosed.
She reportedly told a friend: "Derek saved my life. If he hadn't spoken out to the doctors and told them he thought something was seriously wrong I would probably have died.
"I thought I had a bad case of flu and everyone else agreed. I was even told to stay at home and get some rest. The doctors were so certain it was not serious, and I believed them."
The 27-year-old beauty
was bitten by a mosquito whilst on a trip in Tanzania with the 'Dancing With The Stars' hunk back in June, causing her to fall ill.
After collapsing during a photoshoot, Cheryl was taken to hospital and reportedly sent home after being told she had flu and was suffering from exhaustion.
Hours later Derek insisted she went back to the Cromwell Hospital in West London, where he demanded doctors took out a series of blood tests to discover what was wrong with her - and they learned she had the potentially life-threatening tropical disease.
Derek is now determined to help Cheryl recover and has promised her mother Joan Callaghan he will make sure she eats properly and gets plenty of rest.
A source said: "Derek blames himself for Cheryl getting the malaria and was terrified she was going to die. She's become so important to him, he could not imagine his life without her. He was worried sick and was going without food and sleep he was so concerned. Derek is just thankful she is OK now - and he has vowed to stay close to her so he can do everything he can to make sure she stays healthy.
"Derek has been put under strict instructions to make sure Cheryl eats properly and doesn't overdo it. He has to check in with Joan every day to reassure her. But Joan trusts him and has been really impressed at how he has been there for Cheryl. Derek has been at her side constantly."