The singer - who was ousted from the girl band last month after months of bitter feuds - insists she holds "no hard feelings" towards her former bandmates Amelle Berrabah and Heidi Range, or new member Jade Ewen.
Keisha, 25, said: "I've cried so many tears. I'm over the worst. I believe I am stronger for it all. The girls are my friends. I'm certainly concerned about them and wish them only the best.
"There's no hard feelings with the girls, it's time to move on. I don't want to cry anymore. We all couldn't work together anymore - we weren't happy, me and Heidi. I was depressed. You shouldn't have to go to work treading on eggshells."
Keisha has been supported since leaving the group by her former bandmate Mutya Buena, who exited the band and was replaced by Amelle in December 2005.
However, the 'Overload' singer was quick to deny speculation she, Mutya and third founding Sugababes star Siobhan Donaghy - who was replaced by Heidi in 2001 - are set to work together again.
She said: "Mutya's been very supportive. It's been good to talk with her and have so many friends look out for me.
"We're not forming another band, that is out of the question. But we are friends of course."
Instead, Keisha is now focusing on her upcoming solo album, which she is planning to release in 2010.
She added to Britain's Daily Mirror newspaper: "I'm doing fine - I've been focusing on my solo project and my new look. I've been to Paris Fashion Week and I had the best time.
"I'm really excited about 2010. I'm in the studio working out my new sound - and I'm finally OK with things. I have learned to smile again."
British R'n'B star Taio Cruz recently offered to help Keisha conquer the pop charts on her own.
The 'Break Your Heart' singer - who recently collaborated with Cheryl Cole - said: "I would absolutely work with Keisha if she wanted me to. She can be sure that I will help her out."