Saint Sarah, also known as Sara-la-Kâli ("Sara the Black"...
is the patron saint of the Romani people in Folk Catholicism...
Saint Sarah also shares her name with the Hindu goddess Kali who is a popular deity in northern India from where the Romani people originate"
https://en.wikipedia.org/wiki/Saint_Sarah
She is immersed in the water just as the Hindu goddess Durga is every year in India
There were over 100 Romani-Jewish families in Sofia
https://en.wikipedia.org/wiki/Jewish%E2%80%93Romani_relations