The singer, who was kicked out of the group in 2009, said she was "disappointed" by the treatment she received but wishes the group "the best of luck".
She told Popjustice: "What I will say is that when everyone else found out I wasn't in the group is pretty much when I found out.
"I will say that we had a great relationship, me and the girls; I've never had an argument with Amelle in my life. I was really shocked by the things that they were saying because I'd always been there for them, and they were there for me as well… But, you move on, and you learn, and I learned valuable life lessons during that period."
She explained: "I feel like everything has gone full circle and right now I'm exactly where I'm meant to be. And I genuinely wish them the best of luck.
"To be honest with you I was very hurt and disappointed and I did feel betrayed by the whole thing. But I feel like when you don't forgive people and when you're very bitter it's not really doing anything for you."
Buchanan officially announced today (July 20) that she has reunited with her original Sugababes lineup bandmates, who are calling themselves Mutya Keisha Siobhan.
Watch Mutya Keisha Siobhan perform 'Overload' as the Sugababes in 2001 below: