The singer, who was ousted from the 'Get Sexy' group last month, dismissed speculation that the three-piece are in talks to perform together again.
"Everyone seems to be putting us together & there has been NO plans what so ever ha ha ha... Not in our plans at all lol (sic)," she wrote on Twitter.
Asked to clarify comments made by Buena that a reunion was possible, she replied: "Not sure lol I don't think so, she just said never say never and they took that and ran with it lol."
According to recent reports, Buena has urged Donaghy to put past problems with Buchanan aside and reform the band.
Meanwhile, bookmakers have offered odds of 6/4 that the three singers will release new music by the end of 2010.
Donaghy quit Sugababes in 2001 and was replaced by Heidi Range. Amelle Berrabah joined the group following the departure of Buena in 2005. Eurovision star Jade Ewen became the sixth Sugababe last month.