Speaking to OK!, Girls Aloud singer Nadine Coyle described Harding's death as "devastating".
"When she became unwell, a lot of my energy became focused on her", she said. "There were suddenly so many things happening that were more important than anything else".
"It was a time to be around loved ones and support them. Her passing has just been so devastating", she added. "[Sarah's passing] still affects us deeply, to think about everything that she went through".
Derry singer Coyle has now confirmed that her Nicola Roberts, Cheryl and Kimberly Walsh will reunite to raise money in memory of their bandmate and friend.
"We're planning a night for an event to raise money in honour of Sarah", Coyle revealed.
"We want to raise money for a piece of medical equipment that helps diagnose cancer earlier so people can be treated. We definitely want to do something to help others".
