Girls Aloud star Cheryl has reacted to her former bandmate Sarah Harding's heartbreaking news today.Sarah Harding has been diagnosed with breast cancer, which has spread to other parts of her body.She said on Twitter: "There's no easy way to say this and actually it doesn't even feel real writing this, but here goes."Earlier this year I was diagnosed with breast cancer and a couple of weeks ago I received the devastating news that the cancer has advanced to other parts of my body."In response,