The brunette beauty admits relations with her former Sugababes bandmate - who was asked to leave the group earlier this week when Amelle and Heidi Range complained they were unhappy - became so strained she suffered from depression.
She said: "Keisha didn't leave off her own back - me and Heidi couldn't carry on. You shouldn't have to go to work treading on eggshells.
"Heidi completely supported me and knew what was going on within the band. We weren't happy and it was a struggle to come into work.
"I suppose I was a bit depressed. I needed to be on my own. Even my own family couldn't get hold of me. I hit that wall."
She added: "The problems started in the last few months but it was a long time coming. It wasn't really arguments but the situation got very hard. I'm a chilled person and want to get on with my work and be happy.
"Me and Heidi tried for a long time to make it work, and it got to the point where we couldn't try any more."
However, Amelle is thrilled about the arrival of new bandmate Jade because she feared the fall-out could have caused the band to split for good.
She explained: "We didn't think they'd want to carry on when we said we'd had enough. When met Jade for the first time we all got on well and it seemed natural. It's totally different - we have started enjoying ourselves again and I do feel a bit relieved."
Amelle also claims her recent solo success following her 'Never Leave You' collaboration with Tinchy Stryder could have upset Keisha.
She said: "I honestly don't know if she was jealous of my number one record and everything else that has been happening for me. I don't want to go into airing things, going back and forth. We are adults here and I want to move on and be happy."
The Sugababes have a history of bust-ups within the band and have seen several line-up changes.
Heidi replaced original member Siobhan Donaghy in 2001, while Amelle was brought in after founding member Mutya Buena walked out on the girl group in 2005. Keisha had been the only original member before her departure.