Annette was born Edith Mabel Mills in Wandsworth London. She had originally intended to become a concert pianist and organist, before becoming a dancer, subsequently finding fame as an international exhibition dancer. However, fate struck her a cruel blow when she was forced to retire from professional dancing after breaking a leg. That career over, she turned her hand to songwriting and penned the two popular tunes "Boomps-a-Daisy" and "Home, Sweet Home Again", amongst many others. Some time later, Mills returned to the work of cabaret and revues, and it was while she was on her way to entertain the troops during the Second World War that she was involved in a horrific car accident, which left her hospitalised for the next three years.
Mills is best remembered for being the partner of the puppet "Muffin", in the successful BBC Television children's series Muffin the Mulebetween 1946 and 1955. She wrote the songs and the music, while puppeteer Ann Hogarth wrote the scripts. She made her TV debut in June 1946, when she first appeared with Muffin the Mule, who used to clip-clop around on top of a piano, whilst Mills played a tune. She wrote several Muffin the Mule songbooks and an adventure tale about him, as well as making records.
Later, Mills and Muffin were joined in the BBC's 'For the Children' spot by Prudence the Kitten, Mr Peregrine the Penguin, Sally the Sea-Lion and Louise the Lamb. Although all of the puppets captured the hearts of millions of young viewers, it was Muffin that stole the show. The press commented how he had fired children's imaginations.
Mills's last TV appearance was on 2 January 1955. She died eight days later, after an operation. She had suffered a heart attack.