Alizee is looking a bit tanky here, but she is SINGING. I think she's wearing a jacket to disguise her bulk. A bit overweight or not she looks great to me. And she is SINGING.
Waterloo (Live 2017)
https://www.youtube.com/watch?v=2Voj...J07_7ZJPU9nb-6
With all that vigorous dancing, she might not be singing. She is probably lip-sinking. I wonder if that counts as a break in her refusal to sing? That might not even be her voice.
More speculation: It's unusual for a dancer to put on weight. Could Alizee be pregnant? She said, she and Greg were trying to have a baby.