The 27-year-old, who has Zambian heritage, said on Twitter both she and Beninese singer Angelique Kidjo "made and sang our own edits" and it was "unfortunate" none made the cut.
She added: "I apologise if the lyrics of the song have caused offence. I wish the changes had been kept but that is out of my control."
Lily Allen also said she refused to take part in the project because she felt there was "something smug about it".
She added: "I prefer to do my charitable bit by donating actual money and not being lumped in with a bunch of people like that."
Blur frontman Damon Albarn also appeared to criticise the project, saying "really sometimes, giving money creates another problem".
He added: "Our perspective and our idea of what helps and our idea [of] what's wrong and right are not necessarily shared by other cultures."
The single, which features stars including One Direction, U2 frontman Bono and Ellie Goulding, was originally released in 1984 to raise money to fight famine in Ethiopia.
Critics said it was inappropriate to use the same song - brought to public attention once more by its original creators, Sir Bob Geldof and Midge Ure - for a different crisis.
It has also been pointed out that many of those affected by ebola are Muslim and do not celebrate Christmas.
Others complained the song's revised lyrics, which include the line "there's death in every tear", paint Africa in a negative light.
Sir Malcolm Bruce MP, chairman of the International Development Select Committee and deputy Lib Dem leader, told BBC Radio 4: "Africa isn't a country, it's a continent with many different countries with many different challenges.
"There's a danger that this kind of appeal is slightly patronising and gives the impression that Africa doesn't have the capacity to do things for itself."
Solome Lemma, co-founder of Africans in the Diaspora and the Africa Responds initiative on ebola, told Al Jazeera the original song "created misconceptions about Ethiopia in a patronising way".
And Dawit Gebreselassie, 26, a financial analyst from Ethiopia, joked: "I would ask, does Geldof know when it's Christmas time in Ethiopia?
"Perhaps the fact that we celebrate Christmas a few weeks later on January 7 could have misled him into thinking we don't know when it is.
"Reassure him from us that, after his last three reminders, we are well aware and don't need any more prompting."
Despite the backlash, the single has sold 312,000 copies since its release last week.
Sir Bob, 63, has called claims the song is patronising a "complete load of b*******".
- Daily Mail
