Vedvati
The Queens of Dashrath when got widowed did not do Sati, so, Sati was not in vogue at that time. Even in Mahabharata, the Ambika and Ambalika got children through Niyoga instead of doing Sati.
Vedvati who was a daughter of Sage Kushadhwaja in Kritayuga was approached by Ravana and he proposed her but she rejected him. Angry Ravana grabbed her hair to take her away but through the power of her penance she cut her hair with her hand. She entered fire vowing to come back and destroy Ravana. She was eventually reborn on a lotus and Ravana took the baby but his ministers told him she would be reason of his destruction so he threw the baby in river and she was taken by the river to Mithila where Janaka was ritual ploughing and found the baby in line of a ploughed land and adopted her and called her Sita.
There is also said in retellings that Sulochana, wife of Meghanad and Kumudvati, wife of Kusha did Sati as they couldn't live without their husbands but these stories are not in Valmiki Ramayana but in much later retellings. Sulochana and Kumudvati both were Naga Princesses, Sulochana was daughter of Sheshnaga (Laxmana) and Kumudvati was sister of Naga King Kumud and daughter of Nagas of Sarayu. Both Queens were deeply loved by their husbands.
So, Sati was not encouraged at all, ever in ancient India. Just like how when invaders attacked and women in desperation to save their honour chose fire so that even their dead body won't be molested, so some incidents were just like that. The widows of Dashrath, Ravana and Vali were alive and even moved on with their lives and did their duties. Probably that's why Vedvati chose fire, so that her dead body won't be dishonored by Ravana.