Popi Sidiropoulos worked as a hairdressing apprentice in Greece from the age of thirteen. On arrival in Australia in 1957 with husband Theo, she sat for a Hairdressing examination at the L'Oreal School of Hairdressing in Collins Street, Melbourne. She was awarded the Diploma of Hairdressing with Honours after fifteen minutes of examination in recognition of the high standard of her work. As the only Greek speaking hairdresser at the time, all the young brides travelled long distances to Collingwood to have their hair done at Popi's Hairdressing.

Her husband Theo was elected Mayor of Collingwood on 1 September 1977. According to his daughter, Anthea, he was the first migrant to be elected to that position who spoke English as a second language. Popi became the first non-English speaking Lady Mayoress and and carried out her duties with humour and courage, never losing her faith in humanity. She single-handedly catered for all the mayoral meetings, without understanding the concept of 'catering'. A member of the Australian Labor Party, Theo was elected to the Victorian parliament in the Legislative Assembly seat of Richmond in 1977 and retired in 1988. He was the first non-English speaking citizen to be elected to the state parliament.