Abbie Bloodworth, 19, died after a blaze broke out at a house in Cwmparc, Treorchy, just before 12:00 BST on 19 August.
In a family tribute, her mother, Samantha Dorricott said: "Abbie was my rock, my world and I miss her deeply."
The cause of the fire is being investigated by the fire service and South Wales Police.
"She was a fabulous and loving mother to her three-year-old daughter Chantelle," added Ms Dorricott.
"She was kind, funny and had a heart-of-gold."
A young mother who died in a house fire in Rhondda had "a heart of gold".