Madonna, Babaeng Ahas 1991 on netflix

Merlinda is cursed by her Mother after leaving her father on his death bed to be with her rich lover. Abandoned by all she is now pregnant, destitute, and covered in boils. Merlinda gives birth in a Cave to a human daughter and a snake son. The Baby girl is named Madonna. When Madonna grows up she starts turning into a giant murderous snake. Afraid of losing her lover to the monster she is becoming, Modonna is desperate for answers. Together she and her brother she seek out a cure to their damned existence.